Evolto

Extra-terrestrial Lifeform Evolto (地球外生命体 エボルト), alternately spelt Evolt, was a member of the Blood Tribe who manipulated the power of Pandora Box, a powerful Blood Tribe weapon used to annihilate the civilization of Mars and was the main antagonist of the Kamen Rider Build TV series. He initially operated on Earth using the body of Soichi Isurugi, an astronaut as part of the Kiwami Project, the expedition team that discovered the Pandora Box on Mars. Alongside the remaining three members of the Blood Tribe who had possessed the other members of the Kiwami Project, they masterminded the division of Japan, causing the Japanese Civil War to break out. During his first lookouts on Faust, he had received and used the Transteam Gun to transform into Blood Stalk until he regained his lost Evol-Driver and used his Evolbottles to transform into Kamen Rider Evol, gaining new Evolbottles with each person he possessed. His first later possession came to be Ryuga Banjo before being separated and forcibly absorbed into Sento Kiryu. Soon after achieving his final form, he regained his physical body but continued to take the appearance of Soichi Isurugi, and occasionally Masakuni Mido for public appearances. In his final standoff with the Kamen Riders, he revealed his true form to the general public but continued to take on Soichi's appearance in the Riders' presence, most likely out of habit. After his defeat, his older brother came to Earth looking for revenge.

Early Life on Mars
Takumi Katsuragi claims that before Mars, he has destroyed countless planets. According to Vernage, Evolto's origin are neither terrestrial nor Martian: instead, he is a being from a planet that has yet to be discovered by Earth. Long ago, he used the Pandora Box to raise the Pandora Tower on Mars, forming a black hole that ravaged the planet and ensuring the complete destruction of life on Mars. However, Vernage was able to damage his Evol-Driver and separate Evolto's soul from his body, but Evolto's soul stored itself within the Pandora Box, preserving his essence and energy, albeit fragmented.

Escape to Earth & Planting the Seeds
Thirteen years before the Skywall Tragedy, the nearby planet of Earth sent a probe to Mars. Searching for another planet to destroy, Evolto attached part of his essence to the probe. When the probe returned to Earth, Evolto's essence attempted to possess the first human it saw: Yuri Banjo, a security guard for the probe. However, the essence assimilated with Banjo's unborn son. The child, Ryuga Banjo, was born a month later (a miraculous two-month gestation), sharing Evolto's essence but none of his consciousness nor abilities.

Approximately thirteen years later, the Kiwami Project sent a manned mission to Mars. Soichi Isurugi, one of the astronauts aboard the mission, discovered the Pandora Box in a Martian ruin. Upon doing so, the remaining Evolto essence possessed Isurugi, taking over his body. Creating 60 FullBottles from Isurugi's memories, "Soichi" returned to Earth with his damaged Evol Driver and the Pandora Box.

At the return ceremony for the Martian mission, Evolto triggered the Pandora Box, attempting to use his powers to raise Pandora's Tower. However, Vernage's essence also found a way to Earth, and removed the essence of every FullBottle prior to the ceremony. As a result, Evolto's attempt failed, causing the Sky Wall to rise instead, in what would be remembered as the Sky Wall Disaster. After being medically diagnosed as being "psychologically insane", "Soichi" was arrested and placed in a mental hospital, in which his host's daughter was also admitted into at the same time as well, having been possessed by Vernage in order to stop Evolto. "Soichi" made contact with Shinobu Katsuragi on several occasions to have his Evol Driver repaired as well as to create a new set of Fullbottles, however Shinobu's son Takumi Katsuragi realized the true intentions of "Soichi" and hid the Driver. Several months later, he escaped from the mental hospital and took residence in Touto where he opened up a café called nascita there.

In the following seven years, he was appointed as a special consultant for the Pandora Box, and was asked by Namba Heavy Industries Ltd.'s president Juzaburo Namba to help oversee his underground organization's activities. Evolto arrived at the basement of Namba Heavy Industries Integrated Technology Development Institute, the organization's first lair, in time to see a strange creature attacking the researchers as Katsuragi told them to run. He saw Gentoku reached for the Transteam Gun, stopped him and took the gun himself, firing at the creature with one shot, causing the creature to revert back to normal. Evolto praised for his quick thinking as Gentoku realized he was Soichi Isurugi, unaware he was truly an extraterrestrial lifeform possessing the human. Evolto introduced himself as Soichi to Gentoku as he placed the gun on top of its container and headed down, telling Katsuragi that adjusting the dosage for the Nebula gas administration isn't easy before adding his own calculations to make the dosage safe for administration. After ordering Katsuragi to follow the newly inputted numbers, Gentoku asked him why he was here, which Evolto revealed he worked for Namba, and said he was told by Namba to offer his assistance to Gentoku, Katsuragi and the researchers with their impending experiments. Evolto also mentioned he's the only one who knows full well about the Pandora Box, but Gentoku assured him this research has nothing to do with the box, so Evolto cut to the chase, revealing that he knows what Katsuragi was building isn't a defense system, but the ultimate biological weapon, and that he has plans to use the box to rule all of Japan, which shocked Gentoku. Evolto proposed he could become his right-hand man, but Gentoku doesn't trust him, which lead to Evolto's second proposal: offering Gentoku the power he seeks, and compared Gentoku to Dr. Faust, a scholar whom made a deal with the devil to obtain power. Gentoku asked Evolto that he wants him to sell his soul and retorted by comparing Evolto as Mephistopheles, a demon whom wanted ultimate power. Evolto told Gentoku he'll see soon before exiting the lab, having secretly lay the seeds of his master plan.

During the night, Evolto tracked down the Touto Prime Minister's aide Koji Hotei, killed him and presented his body in front of Gentoku the next day at Namba Heavy Industries' Institute. Stopping dead in his tracks, Gentoku rushed to his deceased friend and tried to wake him, but Evolto appeared from behind Gentoku, telling him Hotei's been dead for a while. Realizing Evolto killed Hotei, Gentoku seized him and demanded to know why he killed him, but Evolto punched him hard in the gut, forcing Gentoku to fall on his knees. Evolto deemed he was acting on Gentoku's wish as he brushed his jacket. Shaking with horror, Gentoku then found clarity and looked up at Evolto with a malicious smile, deciding it's time to make a deal with the devil. He stood smiling as Gentoku rose up, walked over his former friend's body and proceeded to the lab, satisfied his plan has allowed Gentoku to become Night Rogue and create Faust. Some time after, Evolto received a Transteam Gun and a Cobra Fullbottle, allowing him to become Blood Stalk.

Around this time, Misora joined Faust to purify the Fullbottles for them, not knowing it was for evil purposes. After losing the will to do the job when discovering their heinous motives, "Soichi" orchestrated her "rescue" to convince her to purify Fullbottles again while stealing two of the Pandora Box panels from the Touto Institute of Advanced Matter Physics to ensure their confidence. From Faust, he took along a Build Driver and an unknown number of Fullbottles; upon his return, he plastered the panel into one of nascita's basement walls.

In two years, Faust's co-founder Takumi Katsuragi had ascertained the extraterrestrial identity of Evolto and the truth of the Evol-Driver, so he threatened to quit Faust and expose their modus operandi. However, before any progress against Evolto was made, Evolto knocked him out and erased his memories, while at the same time switching his face with the recently killed Taro Satou. He also arranged Nabeshima to lure Ryuga towards Katsuragi's apartment, allowing him to act as the fall guy to "Katsuragi" (Tarou)'s murder. Seeing Katsuragi's high tolerance to the Nebula Gas, Evolto made use of this by arranging a fake encounter on September 5th by putting an amnesiac Katsuragi on the alleyway on a rainy day and renamed him "Sento Kiryu". After his recuperation, "Soichi" indoctrinated both Sento and Misora into fighting Smashes and harvesting their Nebula Gas essence into Fullbottles, all at the same time by watching as Blood Stalk from behind the scenes.

The RabbitTank and Dragon's Intertwined Fate
The morning following Kamen Rider Build, whom has been active for a year, defeated the Needle Smash and saved a freelance journalist, Isurugi was sweeping the front entrance of nascita and proceeded inside when finished until he heard Sento emerging from the secret lab entrance. He hid until Sento fully emerged and greeted him with surprise, and examined the newly created Harinezumi Fullbottle, congratulating Misora for her part in the bottle's purification. Part of his ruse, Isurugi asked Sento if any of his memory came back, to which Sento stated the same few fragments involving a scientist with a gas mask, human testing and a bat-like man. He then amusingly gave Sento his rent, much to the amnesiac's surprise as he had no knowledge of Isurugi charging him to stay at nascita, then surmised it was the reason Isurugi made Sento take the job position at Touto's Institute of Advanced Matter Physics. Isurgi then reminded Sento of this day being his first at the job, realizing he's late. Before he left, Sento unveiled his new invention: the Build Phone and its ability to turn into the Machine Build motorcycle after combining the phone with the Lion Fullbottle. Amazed by his own invention, Sento prepared to drive to work until Isurugi reminded him he's still inside the cafe.

Later on, he learned that one of Faust's test subjects, Ryuga, whom also didn't turn into a Smash after being administered with the Nebula Gas, escaped and informed Sento. Inside the hidden lab, Isurugi gave all the information of Ryuga's background to Sento over the Build Phone. He also stated the scanners for Smash had picked him out and hacked the motorcycle Ryuga was using to gain his coordinates, relaying the location to Sento, knowing full well Gentoku had learned of Ryuga's escape and would send a Smash to intercept and retrieve Rygua.

After learning of making himself an enemy of Touto and bringing Ryuga to their secret lab at night, Isurugi became upset and scolded Sento for this current dilemma he's put himself in. Sento then explained to Isurugi of Ryuga's experimentation by Faust appears similar to Sento's memory and how Sento himself could've been a test subject. To keep up his con, Isurugi then stated if they were both experimented on then they would've both turned into Smash, and how Ryuga didn't lose his memory, leading to the possibility of them finding Faust's lair. However, Sento stated Ryuga can't remembered where the base was, but came up the theory of finding the base by clearing Ryuga's name and finding the true murderer. Isurugi and Sento approached Ryuga, asking him to tell them everything, until Sento and Ryuga argued as Ryuga began his tale from birth while Sento meant the details around Ryuga's incarceration, annoying Isurugi as he walked to his rocking chair by the stairs. As Ryuga told them the cops arrived as he entered the scientist's apartment for a job interview, Isurugi objected to Ryuga's claim, claiming it to be convenient for the cops to arrive at the same time Ryuga found the body. Ryuga claimed it to be the truth until the silver booth went off, unveiling the purified Gorilla Fullbottle.

Isurugi rejoined the group as Misora met Ryuga and Sento proclaimed Ryuga' arrest and jailbreak may be connected until they spotted Sawa Takigawa entering the room, completley unaware that she's one of Juzaburo Namba's children and a spy for Faust. Misora punched Isurugi in the shoulder for leaving the door open, but Isurugi stated he closed the door but realized he left it open, another ruse to kep up his con. He pretended to be even more shocked while Sento was surprised that Sawa learned he was Kamen Rider Build, presenting the nascita match box he dropped the previous night, unaware she took it from the bowl on the counter before entering the secret door. She then claimed she was there to thank Sento, and to want to do a cover story on the Kamen Rider, but Sento declined until Isurugi agreed, much to the annoyance of Sento and Misora.

In the morning, Sento, as Build, responded to a Smash alert, unaware it was a trap to lure him out by Faust. At the location, Build phoned Isurugi to let him know there wasn't a Smash in sight, but Isurugi told him the reports picked up a Smash, until Build realized he walked into a trap set by the Touto government sent to arrest him. After Sento and Ryuga's encounter with Night Rogue and Ryuga's fiance, Isurugi sat outside of nascita reading the Touto Info. on his tablet. Isurugi deemed Sento's fugitive status won't interfere in his plan to purify all of Touto's Fullbottles. He then developed an itch in his back and transmutated his tablet into a glass back scratcher and scratched his back with it, relieving his itch.

Return of the Cobra
Overhearing Sento's explanation of how Masahiro Nabeshima, the man whom gave the job interview with Katsuragi to Kasumi to give to Ryuga, and the same man whom knocked out Ryuga with a sedative as he was selected by Faust as a lab rat, Isurugi entered the lab with flare as Ryuga questioned Misora's capability of finding information on Nabeshima. He told Ryuga not to underestimate Misora and proceeded to help her change into her online idol alter-ego, Miitan. After turning on the camera, Isurugi explained to Ryuga that Miitan is a famous idol over the internet, with hundreds to thousands of fans submitting whatever information she ask. In an instant, they've received information, but of a Smash sighting. Isurugi remained in the lab to monitor any information on Nabeshima while he watched Ryuga argue with Sento as he prepared to head toward the Smash.

After Sento returned with the Flying Smash's essence and have Misora purify it into the Taka Fullbottle, Isurugi told Ryuga what Sento was doing as he placed the Taka and Soujiki bottles in a panel placed in a wall: he was looking for a Best Match. Isurugi said it twice jokingly, and told Ryuga that a pair of Fullbottles have their own affinity as he demonstrated with the Rabbit and Tank bottles, placing them in the panel to show their affinity. He also pointed out each Best Match has its own power, but finding two bottles to form a Best Match is difficult as he placed the bottles back on the table. Sento then joined the explanation, stating his Build Driver was originally an analyzer before it gained the transformation function. Ryuga decided to see if he can find a Best Match, which intrigued Isurugi but Sento doubted it until Ryuga placed the Taka and Gatling bottles in the driver, forming a Best Match. Sento was disbelieved while Isurugi congratulated Ryuga for his "sixth sense", and asked him how he did it, to which Ryuga pointed out that the Best Match can be found with a biotic and abiotic bottles. As Sento argued with Ryuga on how to properly find a Best Match, they accidently woke up Misora, whom threw a knife at the booth and twisted her sleeping mask tightly in her hands, whispering she'll cut them. Horrified, all three men apologized for waking her before Sento headed back to the Touto Institute to find any information on Nabeshima while Ryuga was chained to one of the posts once more.

Near the night, Isurugi learned about Faust's trap to bring Ryuga to Seito by using Nabeshima's family as bait and decided to return as Blood Stalk. He made his way to the Touto Harbor Natsu Wharf, where Sento just defeated the Mirage Smash, which turned out to be Nabeshima. To keep him from waking Nabeshima, Stalk punctured Sento's back with one of his venomous tentacle, leaving him stunned under the poison's effect. Stalk then created a giant energy projection of a cobra and retrieved the incapacitated Nabeshima, leaving Sento to pass out on the ground after seeing Stalk near the smoke. After delivering Nabeshima back to Faust's lair, Stalk returned to the warehouse and brought the unconscious Sento back to nascita, waiting for the poison's effects to wear off before waking Sento by pinching both his cheeks at once before telling Sento he found him passed out from being poisoned and brought him back to nascita to recover. Sento told him it was a man dressed like Night Rogue, but with crimson and a cobra symbol. Before Sento could go any further, he received a call from Ryuga, learning that he and Sawa have made it to Seito. Isurugi heard Sento warning Ryuga that Nabeshima's family being captured by Faust could be a trap for Ryuga after telling him the Mirage Smash was Nabeshima himself. Isurugi asked Sento what he planned to do next after hanging up the phone, but instead Sento told him he gained a new memory fragment where he spotted a green panel with the same markings as the Pandora Box near Night Rogue as Sento was being prepped for the Nebula gas experiment. Sento then theorized that with the box's energy, Faust learned they can create superhuman beings, which Isurugi surmised, to keep up his con, that by solving the mystery surrounding the box would also expose Faust as well. They were interrupted by the silver booth going off, intriguing both Isurugi and Sento enough to see the new purified bottle, the Ninjya bottle. As Misora walked out of the booth and proceeded to bed, Sento asked her to gather information on the Skywall tragedy as Miitan, and after a few exchanges of "pleases" and "don't want to"s, Isurugi changed her clothes to Miitan's, forcing Misora to gather the information until she went to sleep.

After Sento received the information on the Skywall tragedy and returning from the Touto Institute earler than expected, Isurugi prepared to head to his part-time job until Sento brought up how Isurugi wanted him to become Kamen Rider Build, and over the past year Sento hasn't learned anything about Isurugi. Isurugi told Sento he doesn't eat pasta and has a fear of bidets before telling Sento to focus more on the present than the past and left, unaware that Sento learned that he was the astronaut whom brought the Pandora Box to Earth and caused the Skywall tragedy. As part of his plan, Isurugi sent a Smash report as Blood Stalk, stating specifically the subject is a second-dosed Smash, meaning if the element isn't extracted soon the person will die.

Watching Sento, as Build GorillaMond, fight against a Square Smash, Stalk fired a Devil Steam from his Steam Rifle, increasing the Smash's size to a giant's. As Build, in his RabbitGatling Trial Form, struggled against the giant Smash, Stalk informed him from afar that he's injected a new type of gas into the Square Smash, and even if Build saves the person inside, there will be lingering effects. As he watched Ryuga throw a Drill Crusher into the Smash's back, allowing Build to turn into his HawkGatling Best Match and perform a 100 Full Bullet finisher to defeat the Smash, Stalk takes his leave as Sento extracted the Smash essence from Nabeshima, whom was turned into a Smash once more by Rogue to see what would happened to a human being administered the Nebula gas a second time.

Returning to the lair, Stalk was asked by Rogue, who placed the Rocket Fullbottle in their green Pandora Box panel, why he didn't kill Build as he fought the Square Smash. Stalk assured him as the game maker, he derived that not finishing Build will contribute to their overall scheme as time progresses. At night, Isurugi returned to hear a noise at the secret lab, and he rushed to see Sento smashing the wall with the bottle slot with a hammer. Isurugi attempted to stop Sento, but it was too late; the wall was damaged enough for Sento to remove the full slot, revealing it to be one of the green panels from the Pandora Box. Confused and angry, Sento asked Isurugi why he had it and if he's a member of Faust.

Ghosts of the Past
Bringing Sento, Ryuga and Misora to nascita's main interior for a cup of coffee, Isurugi pretended to play dumb as he poured his newly made brew, irritating Sento and making him ask Isurugi again why he had one of the missing panels and if he's a member of Faust. Isurugi joked that he's a member of Faust, irritating Sento even more until Misora told Sento and Ryuga that she was captured by Faust because of her ability to purify the Fullbottles. Isurugi then added he stole the panel and a few bottles as he rescued Misora, all a lie to conceal his identity as Blood Stalk. Sento then unveiled Isurugi as an astronaut from a decade ago, surprising Isurugi that Sento learned of his past as the astronaut whom retrieved the Pandora Box and opened it, causing the Skywall tragedy. Isurugi admitted the box messed with his mind, forcing him to open the box, still wondering why it made him do that. Now playing foosball with Sento, Isurugi admitted he joined Faust, another lie, to gain information about the organization and save Misora, then added that Faust could claw their way into the Touto Institute if Isurugi returned the panel to thoem. Sento asked why Isurugi didn't tell him and Isurugi stated he wanted Sento to become Kamen Rider Build to defeat Faust.

Isurugi stated he wanted to make Faust answer for their crimes, but he and Misora alone couldn't make that happen. He then gave the reason why he didn't tell Sento everything relating to the panel: that Sento would not trust Isurugi, leaving Isurugi with the choice to let Sento discover the panel on his own. Buying his lies, Sento decided to forgive Isurugi, while telling him his coffee tasted horrible. Ryuga insulted Sento for being soft-hearted, but Sento explained that Isurugi wouldn't put much effort in making horrible coffee if he wasn't telling the truth, leading to Isurugi, Ryuga and Misora to try Isurugi's brew, leaving the final verdict that it's horrible. As Isurugi told them they have no define palate, Sawa entered the room with evidence regarding Sento's past, which Isurugi decided it's time to put the next phase into motion.

After learning his true name to be Taro Satou from Tatsuya Kishida, a band member who was Taro's friend, Isurugi transformed into Blood Stalk and sent three Faust Guardians to attack a few contruction workers near the alley he placed the amnesiac Sento a year ago. As three Touto Guardians arrived and destroyed the Faust Guardians, Stalk took control of the Touto machines and had them attack the workers until Sento arrived as Build HawkGatling, destroying the corrupted robots. As he watched the workers run away, Stalk introduced himself properly to Build, Sawa and Tatsuya, saying his name. After Build realized he's the one who turned Nabeshima into a Smash once more, Stalk praised him and gave him a reward: a fight. Stalk and Build trade shots with their Hawk Gatlinger and Steam Rifle until Build managed to force Stalk off of a platform and onto the ground, continuing the fight as Build RabbitTank. Stalk blocked Build's Drill Crusher with his rifle, gaining the upper hand by placing his rifle at an diagonal angle to let the Drill Crusher's blade to roll don with it, allowing Stalk to kick Build. As Build executed a Vortex Finish Rider kick, Stalk cut his foot in midair, shocking Build as he was tossed aside. Stalk praised Build for his kick, but stated he has room for improvement before leaving.

Waiting in the dark at night, Stalk followed Tatsuya underneath a train bridge, listening how Tatsuya blamed himself for Sento's amnesia. With proficient speed, Stalk seized Tatsuya by the throat, squeezing hard until he passed out, bringing him to Faust's lair to be their next test subject. Laughing as he gaze at Tatsuya being prepped for the procedure, he took a spot to sit near Night Rogue, whom asked him why he chose Tatsuya. Stalk's response was to see if Tatsuya would be a worthy opponent for Build as Tatsuya is given the Nebula gas. After Tatsuya turned into the Press Smash, Stalk and Rogue let him loose, leading it to the Touto Institute, while Rogue headed there early as Gentoku to keep to his role in their plan. As Sento stood in a tunnel entrance to the parking lot, watched a squad of Touto Guardians firing at the Smash, Stalk appeared from behind, unveiling the Smash's identity as Tatsuya. He then lied to Sento about Tatsuya volunteering to become a Smash, and as he insulted Tatsuya by calling him a fool, Sento became angry and transformed into Build RabbitTank and attacked Stalk. Stalk and Build matched blows until Build gained the upper hand and performed an even more powerful Vortex Finish Rider kick, injuring Stalk's left hand in the process. Examining the damage to his arm, Stalk deduced that Build's anger has risen his Hazard Level to 3.7, confirming his theory. To Build's surprise, Stalk told him to save Tatsuya while he still can before leaving.

After learning that Ryuga knocked out Sento and readministered the Smash element into Tatsuya, whom then returned to Faust's lair, Stalk informed Rogue of Build's Hazard Level increasing, but Rogue was more concern of Stalk's plan. As Rogue asked him what he has in store, Stalk said he hungers for more strength, and that Build must learn more about himself before proceeding to the next stage. In the morning, Isurugi opened up nascita and blew a kiss at the sun, then proceeded inside to see Ryuga awake, telling him what he learned from Misora last night about his failed attempt to transform with Sento's Build Driver. Grabbing Ryuga by the shoulder, Isurugi warned him not to do it again due to the danger it possesses before Ryuga shrugged him off. Sitting down in a chair, Ryuga asked where Sento was. Isurugi told him Sento went back to the Institute to find Faust's lair so he can rescue Tatsuya, which made Ryuga despondent at the idea of Sento trying to save a friend he can't remember.

Isurugi told Ryuga that's not why Sento's trying to save Tatsuya; Isurugi revealed that Sento is the kind of person willing to help anyone in trouble. As Ryuga mocked Sento for being transcendent, but Isurugi told him Sento's just insecure for having no memory of his life and not knowing who he is, therefore he acts as he is now. He even goes further to say that deep inside Sento is nothing but loneliness that has no end. As Ryuga ponder on Isurugi's words, he drank a cup of coffee Isurugi made for him, shouting it's bitter as he swallows the awful brew. At night, Isurugi received a call from Gentoku, whom informed Isurugi of giving the bait with Katsuragi's data on the Nebula gas generated from the Skywall to Sento, expecting him to find a blindspot to allow him to infiltrate Faust's lair. Gentoku stated that Sento could even surpass Isurugi in intellect, and stated he's looking forward to seeing what happens next.

The next day as Sento and Ryuga infiltrated Faust's lair, Isurugi, as Blood Stalk, shoots one of Faust's human captives to prevent him from leaving and shouting at the other captives to be silent. Ryuga turns to Stalk, lunging at him with a fist as Stalk referred to him as a precious sample. Stalk easily locked Ryuga's arm in his own, allowing him to inject Ryuga with poison, placing Ryuga in agony as dark spots form under his skin. As Sento ran to Ryuga's side, Stalk made a joke about injecting Ryuga with poison, but shrugged it off and stated he still has Sento. Confused Sento asked Stalk what he meant, and Stalk revealed to Sento that he was injected with a large dosage of the Nebula gas, but didn't transform into a Smash, like Ryuga, and it's because of the Smash element coursing within him he's able to transform into a Kamen Rider. With revelation and fury swelling within him, Sento transforms into Build RabbitTank and viciously attacked Stalk, swinging his Drill Crusher all over as Stalk dodged the attacks, destroying parts of the lair in the process. Forcing Stalk in a corner, Build tossed his weapon aside and dragged Stalk to the ground, pummeling him as he demanded to know whom injected him with the gas and erased his memory. As Stalk laughed while Build continues to pummel and demanded to have his memory restored, he told Build he loses perspective when it comes to his lost memory and shot him with his Transteam gun, forcing Build off and cancelling his transformation. He deemed that quality disappointing and decided to end their encounter by firing his gun at the ceiling, compromising the lair. With everyone in danger, Stalk thanked Sento for their brief encounter and left, laughing as Faust Guardians prepared to take the human captives with them.

After viewing the lair's destruction, Gentoku called Stalk, who was waltzing around in their backup lair. Stalk told him Sento now knows of his origin in the lab, leading to Gentoku wondering how long they intend to let Sento run free. Stalk assured him they will end him in time, but for now the next phase of their plan will become more interesting before tossing the phone away, ending their call. After returning to nascita at night, Isurugi sat in his chair as Sawa watched Ryuga gazing at Sento constantly. From Ryuga, they learned that Sento, as Taro a year ago, went to Katsuragi's apartment for a job interview involving new medicine testing. As Sento repeatedly told Ryuga he has no memory of killing Katsuragi and blaming Ryuga for the murder while Ryuga stands by that Sento's the murderer, all four people hear the booth go off. Sento rushed to see the new Panda bottle and walked down, believing that no one else but Ryuga believes he's the true murderer, but Isurugi and Misora played around and pretended to believe he did. Offering a suggestion, Isurugi told both Sento and Ryuga they should investigate into Katsuragi's life.

Returning from the Touto Institute, Sento came up with an anagram to decipher a letter Katsuragi left behind, deducing Katsuragi left his hidden data with his mother, Kyoka Katsuragi. Placing two cups of coffee on a tray, Isurugi proceeded to hand them to Sento, Ryuga and Misora as he listened to Sento's plan to find Kyoka, but to his shock Sento and Ryuga have coffee in cans. He walked toward the back in sorrow, a ploy as he heard from Sawa that Sento and Ryuga can enter into Hokuto by a Skyroad, one of the gaps in the Skywall leading from Touto into Hokuto. However, she stated that Skyroad is governed by a person who won't let people pass without payment. Sento turned to Isurugi, who told him he can't help them as he has a part-time job and can't make decent coffee. With no other choice, Misora used her Miitan persona to acquire the money needed to use Skyroad as Isurugi slumped in a corner beside her.

Returning to Faust's backup lair as Blood Stalk, Isurugi summoned for Gentoku and Utsumi to return, informing Gentoku of Sento's plan to head to Hokuto, telling Gentoku it could disrupt his ultimate scheme: to utilize the Kamen Rider System as a military weapon, and stated if Sento gets caught by the Hokuto government. Gentoku decides to head to the Skyroad and stop Sento. He demands Stalk to accompany him, but he declines, forcing Gentoku to turn into Night Rogue and briefly engages Stalk before subduing him. Stalk concedes and agrees to accompany Rogue.

At the Skyroad passage between Touto and Hokuto, Stalk watched from afar as Rogue and two Faust Guardians intercept a family from Hokuto and the criminal overseeing the passage, calling Sento out as he threatened his captives. With no choice, Sento transformed into Build RabbitTank and duels Rogue, while Ryuga takes on the Faust Guardians, allowing the family and criminal to escape. After Rogue pushed Build into corner and turned to Ryuga, Build brushed him aside with his Machine Builder, forcing Rogue to call on Stalk as Build and Ryuga headed for the passage. Forming his Steam Rifle and inserted the Rocket bottle in the weapon, Stalk performed a Steam Attack, but made it rebound towards Rogue, allowing Stalk to slip away into Hokuto unnoticed.

"As thanks for amusing me, let me tell you something...about Takumi Katsuragi. Katsuragi is the creator of the Smash. Takumi Katsuragi...created Faust!"

- Blood Stalk revealing the Smash and Faust's creator to Build and Ryuga.

Watching Sento and Ryuga talking to Kyoka as three of her students left, Stalk sneak-attacked the children, forcing Sento, Ryuga and Kyoka find Stalk standing over Takehiko, one of the students. Stalk told them he learned of their plan to find information on Katsuragi and told them to play with him as unleashed a Devil Steam with his Steam Blade, turning Takehiko into an Ice Smash. Ryuga asked how Stalk turned the kid into a Smash, and Stalk revealed his blade can administer Nebula gas into a human without Faust's equipment, angering Sento as he transformed into Build NinninComic, attacking Stalk and the Smash. Build used the 4Koma Ninpoutou's One Frame-Clone technique to split into two, leaving him to fight Stalk as his copy used the Four Frame-Steal technique to bring the remaining two kids to Ryuga and Kyoka before engaging the Ice Smash. After defeating the Smash and telling Ryuga to extract the element from Takehiko, the clone Build assisted Build as he fought Stalk until the clone disappeared, leaving Build to fight Stalk alone as Ryuga and Kyoka took the children to safety.

As Build turned into his PandaGatling Trial Form, Stalk combined his Steal Blade with his Transteam Gun, then proceeded to place the Rocket bottle in the Steam Rifle and executed a Steam Attack, forcing Build out of his transformation and the Gatling bottle out of the Driver. As Stalk proceed toward the Gatling bottle, Ryuga attempted to engage Stalk but is easily caste aside, but the Cross-Z Dragon reached the Gatling bottle first and placed it in its back, allowing it to fire pellets of blue fire at Stalk. Ryuga took the chance to fight Stalk, but instead ended up removing the Rocket bottle from the rifle in a scuffle, and proceed to give it to Sento. Transformed into his new RocketPanda Best Match, Build overpowerd Stalk and performed a Vortex Finish Rider slash, forcing Stalk in a corner. Stalk, however, became amused as Build's strength increased once more, and left a parting gift to Build and Ryuga: Katsuragi is the creator of the Smash and Faust, and questioned their next move as he left via typhoportation.

Back at Faust's backup lair, Stalk was approached by Gentoku, whom returned from a meeting between the three Prime Ministers, and demanded to know why he made such a mess in Hokuto. Stalk assured him it can lead them to the thing they've been searching for years: Katsuragi's research data, and with it, they can upgrade the Rider System to a new level. The next day, Stalk observed from a distance as Sento and Ryuga found the location of Katsuragi's research data: at the abandoned Namba Heavy Industries Integrated Sciences Laboratory. Seeing Sento and Ryuga pulling out a flash drive from a buried container, Stalk revealed himself, stating he'd never thought Kyoka would hide her son's research in an abandoned building as he took the flash drive and tossed Sento and Ryuga aside. As Stalk thanked them, Ryuga attempted to fight him, but Stalk pushed him aside, forcing Sento to transform into Build HawkGatling and engage Stalk. From a nearby tree, Gentoku transformed into Night Rogue and joined the fight, engaging Build as Ryuga lunged toward Stalk again. Rogue told Stalk to let him fight Build, which Stalk obliged as he attempts to leave, but Ryuga engaged him once more. Catching Ryuga's fist, Stalk notices his Hazard Level has risen to 2.4, deciding to fight him for a while. As they fight, Stalk measured Ryuga's Hazard Level rising to 2.5, then 2.6 and 2.7, relishing in how it continues to rise. Tossing Ryuga aside, Stalk decided to hand him the driver, stating he wish to see how Ryuga progresses before intervening in Rogue's battle with Build, allowing him and Ryuga to escape. Rogue pointed his Transteam Gun at Stlak, demanding to know Stalk's scheme, to which Stalk assured him they don't need the driver, just the tools the data can create as he believes both Sento and Ryuga can do it.

Faust Invades Touto Institute
"Don't get the wrong idea. The Rider System was designed to be a military weapon to spill gallons of blood! Principles as a scientist? That's just your ego talking. I'm sure you understand that science leads to destruction. As science progresses, humanity regresses...the environment is destroyed and the world perishes!"

- Stalk stating his view of science to Sento. Watching Katsuragi's introduction video on the Build Driver and Kamen Rider Build form with Sento and Ryuga, Isurugi attempted to act hip with slangs as he commended the video. Ryuga asked him why he's talking like that, and Isurugi told him a girl in his part-time job was teaching him before reminding Sento he stole the Build Driver, the Fullbottles and the Pandora Box panel they had from Faust. He also added he tried to use the driver to transform, but nothing happened, and Sento told him only a person with a Hazard Level over the base level could transform and explained to Isurugi the different levels of people with Nebula gas resistance: Hazard Level 1 where the person injected with the element would die soon afterward, Hazard Level 2 leads to the creation of the Smash, and people with a level over 2 are those who retain their human forms, to which Isurugi realized both Sento and Ryuga are at that point. Ryuga then pointed out that Stalk measured his Hazard Level as it rose during their previous encounter, leading Sento to conclude that a person with a Hazard Level 3 can transform into a Kamen Rider. Isurugi asked Sento if Katsuragi said anything else in the video, but Sento stated that Katsuragi was looking for a person who fit all the requirements to become Build through his human experiments with the Nebula gas. Isurugi then took notice of Sento and Ryuga arguing over the Smash experiments, leading to many casualties. As Ryuga blamed Katsuragi for seeing people as nothing more than guinea pigs and for the death of Kasumi, while Sento believed the science in the experiments were not at fault, Isurugi took his cue to leave.

After figuring out Ryuga took Misora sightseeing outside nascita, Isurugi, as Blood Stalk, informed Faust, sending Faust Guardians to their current location. Stalk arrived in between Ryuga and Night Rogue with Misora passed out, telling Rogue to not act behind his back. As both Faust members star at each other, Ryuga picked up Misora and fled, Rogue attempted to pursue but Stalk stopped him, unaware that Rogue had Faust Guardians corner Ryuga, only for them to be destroyed by Build NinninComic. Returning back to the lair, Stalk demanded to know why Rogue plotted behind his back, forcing Rogue to tell him that Juzaburo Namba, president of Namba Heavy Industries Ltd. and the benefactor of Faust, gave the ultimatum of giving him the Rider System or he will ally himself with either Seito or Hokuto. Cancelling his transformation, Gentoku stated he must keep the Rider System from being distributed to other countries as well, leading to Stalk asking him what he'll do. Gentoku then decided to take the Pandora Box from the Touto Institute, hoping it will cause a spark between the three regions to declare war.

The next day, Stalk waited patiently with a platoon of Faust Guardians in the the Touto Institute at the garage level. While Shingo Kuwata distract Build, Eita Kawai disengaged the security lock to the garage level, then proceeded forward in the Institute. Making his way to the entrance floor, Stalk injected four security officers with a poison that disintegrates their bodies, killing them instantly. Turning to a security camera over his right shoulder, he signaled Kawai to trap the three Prime Ministers, Utsumi, two security officers and the Pandora Box in an energy dome until he reached the eleventh floor where the box was placed on display. Along the way, he was shot at from behind by Touto Guardians and Touto Special forces, annoying him to snap his fingers and convert the Touto Guardians into Faust Guardians. As he reached the eleventh floor, the dome dispersed, allowing Stalk to proceed toward the Pandora Box. He killed the two security officers with his poison and commented on all the Prime Minsters being together before telling them he'll take the Pandora Box. Tajimi, Hokuto's Prime Minister, attempted to defy Stalk, whom pointed his Transteam Gun at her before firing at the security cameras.

Taking the Pandora Box, Stalk made his way to the roof until Ryuga, disguised as a Touto Security officer, approached behind him. Stalk commended Ryuga for being gutsy as the Faust Guardians engaged Ryuga, whom defeated all of them with the power of the Dragon bottle. Intrigued by Ryuga's power, Stalk attempted to fight him until Kawai appeared, telling Stalk to leave Ryuga to him. Obliging Kawai, Stalk infused him with the Devil Steam from his Steam Blade, turning Kawai into a Press Smash Hazard and leaving Ryuga to fight the Smash. On the rooftop, he heard Gentoku's voice from behind, turning to see him. As Gentoku held his Transteam Gun, he told Stalk the roof wasn't in their escape route. Stalk attempted to lie about getting lost, but Gentoku saw through it as he noted Stalk's scheme to shoot out the security cameras to cover his tracks. Transforming into Night Rogue, he asked Stalk to handover the box, to which Stalk declined, annoying Rogue and forced him to engage Stalk. Ryuga, with a few cuts and bruises, interrupted their fight. Stalk asked him what happened to the Smash, and Ryuga stated he beat it but couldn't extract the Smash element without an empty Bottle. Rogue was shocked Ryuga managed to defeat a Smash without a Rider System, while Stalk became amazed.

Ryuga then engaged Stalk, only to be quickly defeated as Ryuga's fight with the Smash left him scathed until Build HawkGatling arrives to assist him, forcing Rogue to assist Stalk. Rogue fights Build while Stalk engaged Ryuga once again. During the fight, Stalk told Ryuga his attacks won't hurt him until they started to cause damage. After Ryuga punched his left arm, Stalk realized Ryuga's Hazard Level has risen to 3.0, praising him for finally awakening his full power. However, it wasn't enough as he knocked Ryuga down, which was caught by Build FireHedgehog, whom ceased his attack on Rogue and attacked Stalk with fire. While Rogue sneak-attacked Build, Stalk inserted his Cobra Fullbottle in his Steam Rifle and executed a Steam Shot at both Rogue and Build, knocking Rogue to a wall and not only cancelling Build's transformation but force him to drop the majority of his Fullbottle collection as well. As Rogue recovers, Stalk takes the Pandora Box and leaves, angering Rogue.

On ground floor again, Stalk noticed the defeated Press Smash Hazard approaching him. Surprised it can still move, Stalk inserted his Cobra bottle into his Transteam Gun, executing a Cobra Steam Break shot, finishing the Smash long enough for Stalk to extract the Smash element from it, reverting it back to Kawai. As he walked away, Kawai asked him if he was Katsuragi, which Sento heard as he caught up to Stalk. Kawai thought Katsuragi faked his death because he was planning something huge, but Stalk assured him Katsuragi is dead. Refusing to believe that Kawai stated Katsuragi could've used modern technology to transfigure a corpse. Intrigued, Stalk walked over and demonstrated such ability, by painfully transforming Kawai's face into Kuwata's. As Sento rushed to an unconscious Kawai, Stalk leaped into a Faust Guardians' Union State, turning it red and fleed, with Sento, transforming into Build RabbitTank and on his Machine Builder, pursuing him. Stalk attempted to lose Build by shooting at him, but Build managed to destroy one leg with the Machine Builder's front wheel forming a spiked energy wheel, then taking heavy damage from Build's Drill Crusher gun mode before being finished by the Machine Builder's axle saw, forcing Stalk out of the gestalt machine.

In pain from the explosion, Stalk turned to Sento, whom believed Stalk was Katsuragi, and was asked why he faked his death, framed Ryuga and injected Sento with the Nebula gas. Stalk asked Sento if that's what he shoul really be asking, forcing Sento to ask him why he created Faust, the Smash, and if the Rider System was a tool to protect the innocent. Disgusted by Sento's words, Stalk pushed him down and told him the Rider System was a military weapon for bloodshed and scoffed at Sento's claim of a scientist's principles and added science leads to destruction, which is evident by humanity's actions on the world with the environment being destroyed. Sento doesn't believe that and said if used properly, science can bring people happiness, but Stalk asked him if he was sure, and reminded him of the Nebula gas experiments harming lives until Rogue knocked Sento out from behind. Rogue asked Stalk where he planned to take the Pandora Box as a dozen Faust Guardians surround them, their rifles pointing at Stalk. Stalk told him to their lair as he offered the box. Rogue then took the box, and grabbed Stalk, gesturing to him to not try a stunt like that again, and stole the Rabbit, Tank and Lion bottle from an unconscious Sento. Stalk watched as Sento came to and grabbed Rogue's leg, demanding his bottles back before Rogue kicks him in the face, then proceeded to walk away laughing.

Rise of Cross-Z & Cover Exposed
Despite showing Gentoku he was still with Faust, Blood Stalk was not informed of where the Pandora Box was placed, forcing him to infiltrate the Touto capital, marching in on Gentoku and Utsumi after a meeting with Tajimi and Mido. Utsumi attempted to halt Stalk, but he pushed him aside, continuing to walk toward Gentoku, whom told Stalk to leave. Stalk made a comment about Gentoku's temporary position as acting Prime Minister has made him cold and asked why Gentoku placed the box in a secure location without informing Stalk. Gentoku told him if he plays nice, he would reveal the location, which irritated Stalk as two Touto officers barged in the room, preparing to arrest Stalk. Stalk, however, killed them both with his disintegration poison before telling Gentoku that Faust doesn't belong to him.

Finding out Gentoku set a trap for Sento and Ryuga to take the Dragon and Lock bottles, Stalk went to the abandoned warehouse in time to see Gentoku, as Night Rogue, stand a few feet away from Ryuga and a defeated Sento. Stalk praised Rogue for acting behind his back, but Rogue was upset Stalk found out about his plan. Ryuga argued with Sento as he took his Dragon bottle back in an attempt to transform and expose Stalk's identity, but Stalk assured him he came to help them, but Ryuga doesn't believe Stalk, saying he's the one who framed him and vowed to defeat as he attempted to place the Dragon bottle in the Cross-Z Dragon, but failed. Annoyed, Stalk told Sento to take Ryuga and leave, throwing a canister at Rogue who attempted to shoot them with his Transteam Gun. As Rogue asked Stalk why he stopped him, Stalk scoffed and left, leaving an angry Rogue walking out of the warehouse.

After Ryuga transformed into Kamen Rider Cross-Z and defeated the Octopus Smash, whom was revealed to be Sawa, Isurugi was with Misora, Sento and Ryuga as Sawa confessed she was a spy for Faust and Namba Heavy Industries. She also revealed that she already knew about the secret lab's entrance and grabbed a matchbox from the bowl to back up her lie that Sento dropped a mathcbox the day he rescued her. As both Sento and Isurugi celebrated that they didn't leave any tell-tales of the lab, Misora cut them off and told Sawa to continue, and Sawa revealed her job was to get close to them and pass along any information to Namba's company. Isurugi then explained to everyone that on the outside, Namba's company is the top industrial leader, but in reality they manufacture weapons, smuggle goods and other illegal dealings. He even adds that the three Prime Ministers can't go against Namba before Sawa revealed that Namba is a benefactor for Faust. Ryuga doesn't believe Sawa's claim, and Sento added if Namba was Faust's benefactor, then Faust knew about nascita being a front for Kamen Rider Build from the get-go and asked Sawa why Faust didn't attack them. Sawa stated they didn't attack nascita because they wanted to gather data on Build so Namba can use the Rider System for warfare. Sawa then claimed she was acting as Faust's spy to gain information on them, which she backed up with a chip in her necklace, which is a recording file of a conversation between Rogue and Namba while she was abducted before her transformation into the Octopus Smash. In the recording, it mentioned the location of the Pandora Box, which leaves everyone puzzled on where the location is. Isurugi stated it can't be back at the Touto Institute, and Sento wondered where the box was before it was placed in the Institute, which Sawa revealed it was at Namba Heavy Industries Integrated Science Laboratory before the lab was abandoned.

Isurugi, as Blood Stalk, walked in on Night Rogue, Kamen Rider Cross-Z and Sento, finally figuring out the box was placed in the third basement in the abandoned laboratory. Rogue demanded to know why Stalk came, to which Stalk replied, to Rogue's surprise, to fight him. As they fought, Stalk spotted a newly paved wall and thrusts his Steam Blade in it to create a hole, exposing not only the Pandora Box, but the Fullbottles Rogue stole from Sento, the new Densya bottle and Faust's Pandora Box panel. Rogue pushed Stalk away from the box and bottles, allowing Sento enough time to retrieve his bottles and transform with an additional Build Driver into Build KaizokuRessya. As Build intervened in their fight, Cross-Z forces Stalk down the hall as Rogue and Build engage one another. Cross-Z claimed to Stalk he'll unmask him as they fought, forcing Stalk on the ground from Cross-Z's Beat Closer Million Hit slash. Rising, Stalk praised for Cross-Z and decided to leave with the Pandora Box via pyroportation.

Returning to nascita at night after making a deal with Namba, Isurugi went into his act and became surprised and happy to see all of Sento's Fullbottles and the second green panel in the lab. Isurugi praised Ryuga and Sento, but he was confused to see Sento building something, which Misora revealed it to be new weapon, which was inspired by his new Best Match: Kaizoku Hassyar. Finished, Sento swung his new weapon at Isurugi, who ducked down screaming frantically, then at Misora, Ryuga and Sawa before attempting to test the weapon's capability on Isurugi, who ran behind a beam as he told Sento not to point it at him as Ryuga grabbed Sento. The next day as Namba's contigency to destroy Faust was commenced, and Utsumi was a scapegoat for Gentoku as Night Rogue and as the creator of Faust, Stalk saved Utsumi after Gentoku shot him off a bridge, dragging him to land from a river.

At night, Isurugi returned to nascita, finding Ryuga, Sawa and Misora confused as Sento was left alone in the secret lab. Isurugi asked Sento if he was alright through the fridge door, completely unaware that Sento was upset after learning from Nabeshima, whom recovered his memory, that Isurugi is Blood Stalk. Attempting to drawn Sento out, Isurugi made grilled horse mackerel and fanned the odor, which drew Sento from the lab with a smile on his face. As Sento leaned against a column, Isurugi asked him if Nabeshima really called him, to which Sento confirmed and revealed that Nabeshima also regained his memory. As Ryuga asked Sento if Nabeshima remembered who framed Ryuga, Sento stated Nabeshima was just following orders from Stalk, but unaware to Isurugi, Ryuga, Misora and Sawa, Sento concocted a plan to confirm if Isurugi was Stalk.

The next day, Isurugi received a summons from Gentoku and arrived as Stalk, meeting Gentoku in the woods. As Stalk pointed out it's not like Gentoku to call for a meeting, he demanded the location of the Pandora Box from Stalk, which Gentoku learned that Namba was cutting him out of their deal with the Rider System the previous night, but Stalk joked about Gentoku being straight to the point. Angering Gentoku, Stalk decided to reveal the location, but in return he wants Gentoku to swear loyalty to him, which infuriated Gentoku even more to transform into Night Rogue and settle the score with Stalk once and for all. Stalk asked Rogue if thinks he can win against him as Rogue mentioned the Transteam System, unlike the Rider System, keeps the user's Hazard Level at a fixed level, making them both equal as Rogue made the first move. Rogue gained the upper hand with his bat abilities, Steam Blade and Transteam Gum, forcing stalk to the ground until he decided to let experience determine the outcome as he slipped under Rogue via typhoportation and summoned his Steam Rifle, overpowering Rogue with a combination of assaults and blasts, forcing Rogue out of his transformation. As he pointed his rifle at Gentoku, Stalk decided to reveal that he made a deal with Namba and became his new partner, meaning the box is located at Namba Heavy Industries. He then pointed the predicament Gentoku is now in if he utilizes the Touto government to secure the box, which will lead to Namba siding with Seito or Hokuto and declaring war. As he walked away, Stalk mentioned if he was in Gentoku's predicament, he should use someone unconnected to the Touto government, hinting Sento.

Returning to nascita at sunset, Isurugi spotted Sento sitting by the front counter, asking him what's wrong. Sento changed the subject by welcoming Isurugi back and asked him if he'd just returned from his part-time job, to which Isurugi confirmed and said he'll be heading back there tomorrow. Sento made a joke about which of Isurugi's job is real, and Isurugi stated he's just trying to keep nascita open, even when no customer has come for a cup of coffee. Isurugi revealed that nascita is a special place and asked Sento if he remembered the day Isurugi found him and became Kamen Rider Build. Isurugi stated from that day, nascita was Sento's home, and he admitted he'd like to welcome Sento back after his fights with the Smash, making him, Sento and Misora a family.

As Isurugi expected, Sento and Ryuga broke in the 7th Touto plant of the Namba Heavy Industries to infiltrate the massive storage facility, which Gentoku informed Sento that the facility is where the Pandora Box was located. Waiting in a screening room with the box, Isurugi, as Blood Stalk, tampered with the door, allowing it to open as Sento and Ryuga, as Kamen Riders Build KaizokuDensya and Cross-Z, failed to open the door. As both riders entered the room, Stalk informed them the door's password changes every three hours, which is something Sawa should've noticed during her reconnaissance of the Touto plant. Build asked if Stalk let them in to tell them that, but Stalk shrugged it off, saying he doesn't need to thank him and admits he takes pleasure in toying with them. An angered Cross-Z made the first move as Build hesitated before assisting him against Stalk. To the riders' surprise, Stalk was able to counter their every moves, deflecting Build's Kaizoku Hassyar's shots with his Steam Blade and send him sliding aside as he engaged Cross-Z. Build transformed into HawkGatling and rejoined the fight, adding aerial assaults as Cross-Z continues his assaults, but Stalk grabbed him and used him as a shield against Build's HawkGatlinger's shots. Spotting an opening as Build hovered over Cross-Z, Stalk formed his Steam Rifle and shot Build down, who then transformed into Build NinninComic and used his 4Koma Ninpouto's duplication jutsu, gaining the upper hand until Stalk inserted his Cobra bottle into the rifle, executing a Steam Shot that took out the Build duplicates before knocking Build down.

After demonstrating his strength, Stalk told Build whatever tactics and attacks with each Best Match is futile for Stalk knows all of them. As Build rose, Stalk was confused to see a new bottle: Octopus, and with the Light bottle, Build transformed into a new Best Match form: OctopusLight. Build utilized the BLD Light Bulb Shoulder and Shade Breaker, blinding Stalk as he attack him with his Twist Lash Arm, overpowering Stalk before tossing him across the room. As Cross-Z rejoined the battle, both he and Build executed finishing attacks: Build with a Vortex Break Rider punch and Cross-Z with a Lock powered Mega Slash from his Beat Closer, bring Stalk down to the ground. Cancelling his transformation, Sento revealed to Stalk that he wouldn't be able to anticipate Sento's attack with a new bottle. Stalk admitted he was surprised to see a new bottle, but then he pointed out all of Touto's Fullbottles have been purified, which was Stalk's goal all along as he prepared to leave. Before he could, Cross-Z attempted to stop him, forcing Stalk to unleash a energy cobra from his symbol, which distracted the riders long enough for Stalk to leave via typhoportation, and leaving the Pandora Box to Sento and Ryuga.

At night, Isurugi returned to nascita, heading down the lab to see the Pandora Box in the middle of the lab. Pretending to be surprised, Isurugi commended both Sento and Ryuga for their work until he spotted them, with Misora, eating a large banquet with the money from the cash register, desolating Isurugi. Ryuga stated Isurugi wasn't using the money, forcing Isurugi to join in their feast. As Misora and Ryuga slept, Isurugi took the eighteen of the twenty bottles, both green panels and the Pandora Box, existing the lab and proceeding out the front door until Sento stopped him, and both realized the jig is up. Sento revealed that Nabeshima remember Isurugi's true identity as Stalk, but Isurugi demanded proof as he pointed out that Nabeshima could be lying. Sento also agreed, but he came up with a plan to confirm Nabeshima's claim: by having Misora purify the Octopus bottle in secret, which also revealed to Sento that the reason Stalk was always aware of Sento's plan was because he knew about them. Isurugi commended Sento for his ingenuity, but Sento wanted to hear from Isurugi's words that he is Blood Stalk. Turing to Sento before smiling, Isurugi bursted out of nascita, forcing Sento to pursue him.

"Let me tell you one more thing. Watch out for Gentoku Himuro. He's actually Night Rogue. You can have the Pandora Box. I can take it back anytime. What's important...is how much you've both grown. Do your best and grow strong. Ciao!"

- Evolto reveals Night Rogue's identity to Sento and Ryuga.

Isurugi ran a long distance with Sento on his trail until he collapsed near a bridge, panting from exhaustion as Sento caught up to him. As Isurugi made a claim about getting old, Sento asked him why he did this, make Sento into Kamen Rider Build to defeat the Smash when Isurugi was part of Faust the whole time, which Isurugi revealed it was all part of a larger scheme he had. He jokingly asked if Sento would let him go, but he knew Sento wouldn't. Accepting it, Isurugi also pointed out he still need to get the Octopus and Light bottles, which Sento realized Isurugi lead him to the bridge away from pedestrians. Claiming to go all out, Isurugi pulled out a Transteam Gun and the Cobra bottle, which confirmed he is Blood Stalk, and transformed. Stating he is Stalk, Isurugi activated the suit's voice modulator since he only spoke through it when he was Stalk. Sento transformed into Build OctopusLight and attacked Stalk with the Twist Lash Arm,which was blocked by Stalk's Steam Blade. Pushing Build back, Stalk made a comment about the Octopus bottle being the most annoying due to his hatred for octopi as Build executed a Vortex Break Rider punch, driving Stalk back. As Build ran toward him, Stalk pulled the Pandora Box from his pouch and cast a blinding light, followed by energy, at Build, which cancelled his transformation and knocked the Octopus and Light bottles out of his Build Driver. Retrieving the last two bottles, Isurugi cancelled his transformation, satisfied he now has all the Touto bottles, the green panels and the box, bidding farewell to Sento as he left, completely unaware that Sento switched all the twenty bottles with fakes and that one of the empty bottles, that fell from Sento's jacket, had absorbed the energy from the box.

The next day, Isurugi presented the box, green panels and twenty bottles to Namba, informing him all the Touto bottles purified and asked he wants to do with the box when it's opened. Namba revealed that he wants the energy within the box to create a weapon surpassing a nuclear bomb, thus solidifying Namba Heavy Industries' position as the number one weapons manufacturer, which Isurugi found scary. As Namba placed the Rabbit bottle in one of the green panels, it didn't light up but played a recording of Sento's voice saying "Mismatch", which was followed by the remaining nineteen doing the same thing, shocking both Namba and Isurugi as they realied they're fake. Isurugi grabbed the fake Gorilla bottle, which ejected a blue flag with "Too Bad" in japanese kanji; Isurugi commended Sento for being ahead of him this time. Later on in an abandoned storage facility, he called Sento, stating he need to settle things with him before taking his plan to the next stage, which Sento agreed and both decided to meet in the alley Sento, as an amnesiac Katsuragi, met Isurugi for the first time.

While it rained, Isurugi, with the Pandora Box, waited in the alley until Sento arrived, claiming this scene is nostalgic as he placed the box down. Sento asked Isurugi if the entire time he spent with Sento, Ryuga and Misora was all a lie, to which Isurugi said that some of their time together wasn't a lie, commenting on how Sento's development made Isurugi feel bad for deceiving him. Infuriated, Sento tossed his umbrella aside and put on his Build Driver, inserting the Rabbit and Tank bottles in the belt. Isurugi obliged Sento by tossing his umbrella aside and pulled out his Transteam Gun, inserting the Cobra bottle in it and transformed at the same time Sento did. Both Build and Stalk stared at each other before lunging toward one another, their punches casting a shockwave for a moment before they begin to fight. Being stronger, Stalk forced Build into a construction facility, trading blows with Build until he gained the upper hand. As Stalk prepared another punch, Build countered with a Vortex Break attack from his Drill Crusher with the Ninjya bottle inserted in it, driving Stalk back until he drew his Steam Blade and continued his attacks. Both fighters continue to trade blows until Build stopped, due to his memories with Isurugi, allowing Stalk to savagely assault him with his Steam Blade and Transteam Gun, forcing Build out of his transformation as Sento fell to the ground. As Stalk shook his head in dissatisfaction, Sento, filled with sorrow, confessed he can't kill Stalk as he was the one who made Sento the man he is now after his amnesia. Stalk, however, showed no similar emotion and stated, with his voice modulator off, that the battle's over as he pointed his gun at Sento until it was knocked out of his hand by Ryuga's Beat Closer.

Turning to see Ryuga, whom overheard the conversation, decided to fight in Sento's place and transformed into Cross-Z, fighting Stalk as he stated his anger doesn't come from his framing by Stalk, but of how Stalk manipulated both Sento and Misora. As Cross-Z continued his assaults, Stalk retrieved his gun and inserted his Cobra bottle in it, executing a Steam Break shot, sending Cross-Z back and cancelling his transformation. Before Sento rushed to Ryuga's side, Stalk asked Sento why he didn't find it strange that he rescued Misora from Faust, and asked Sento to become Build to fight the Smash. To Sento's shock, Stalk revealed that it was all to make Misora purify the Fullbottles by making her believe it was for justice as she refused to purify them after learning Faust was using them for malice purposes, even when threatened she still refused. Stalk then approached an angered Sento that his role as Kamen Rider was just to help Misora purify the bottles for justice, while in reality Sento was a puppet as he grabbed Sento by his jacket before tossing him back down. As Stalk revealed how far his manipulation ran, he also added to both Sento and Ryuga they can't defeat him. Stalk then turn to Sento, whom accepted to being deceived but that both him and Ryuga weren't puppets, they fought to protect others and grow their strength, and to protect people. Sensing Sento's new resolve, Stalk paid no attention until he spotted a new item Sento pulled out, the RabbitTank Sparkling bottle, which Sento placed in his Build Driver and transformed into a new form: Build RabbitTank Sparkling.

Leaping forward with heightened speed, Build delivered a powerful kick to Stalk, forcing him back. Stalk attempted to counter with a few punches, but Build blocked them and attacked Stalk with stronger blows. Stalk tried using his Steam Blade, but Build knocked it from his hands and continued with power counters, forcing Stalk to a beam. Commending Build's new power, Stalk, with his voice modulator turned on, summoned two energy cobras from his symbol, but Build was stronger than them and forced them out through the roof. Heading outside, Stalk was shocked to see how strong Build became, whom then executed a Sparkling Finish Rider kick, destroying both cobras and sending Stalk, whom attempted to block the attack, flying back to the alley as he transformation came undone. Isurugi, struggling to rise, couldn't believe he was beaten by Build, whom arrived and cancelled his transformation, severing all ties to Isurugi. Isurugi commended Sento for his actions and added that if Sento was able to build the RabbitTank Sparkling bottle, then he can complete a new device in Katsuragi's research data. Before leaving, Isurugi revealed to both Sento and Ryuga that Gentoku is Night Rogue and decided to leave the green panels and the Pandora Box with Sento, stating that he looks forward to see how both riders will progress in future events as he bid them farewell and leapt out of the alley.

Enigma Crisis
"The current situation isn't exactly good for me, either."

- Evolto When the world was threatened by the Enigma device, linking it to the parallel World of Ex-Aid, Evolto, though not intervening directly, took steps to ensure it did not end prematurely. Returning to nascita, "Soichi Isurugi" interrupted a confrontation between Sento and Parado, a Bugster from the World of Ex-Aid. Snatching the Doctor and Game Fullbottles that had been acquired from Ex-Aid's essence extracted by Takumi Katsuragi, "Soichi" revealed to Sento that the new monsters that had emerged were a hybrid organism created by Nebula Gas infused with the Bugster Virus, and that only Kamen Riders with the power of video games could stop them.

Lending the Game Fullbottle to Parado, "Soichi" allowed him to communicate with his homeworld, learning that only a week had passed there while he had been stranded in Build's World for two years, with "Soichi" deducing that the timelines of the worlds ran differently before being brought into sync by Enigma. Learning that Ryuga was now in the World of Ex-Aid, "Soichi" realized that he had crossed-over via Enigma. When Parado passed out, "Soichi" noted that, as a virus, the Fullbottle's caused a negative reaction in him. Leaving the Doctor Fullbottle to Sento, "Soichi" assured him that Parado feel better in no time. Explaining the source of his knowledge to Sento, "Soichi" revealed that Kaisei Mogami, a researcher for the Touto government, had published a paper theorizing that the Sky Wall could be used as a means of travel to parallel worlds, deducing that he was behind the current crisis.

Entrusting Sento to stop Mogami and save the world, "Soichi" left to him the Phoenix and Robot Fullbottles, acquired from Hokuto. When asked by Sento as to why he betrayed him, "Soichi" told him that was a story for another time as he took his leave, disappearing before Sento could pursue him.

Hokuto Declares War on Touto
Days after the Enigma Crisis was averted, Evolto watched from the shadows in the Touto Institute's parking lot as Sento and Ryuga confronted Gentoku in a plan to expose his identity as one of Faust's creators Night Rogue. After Sento and Ryuga left, due to Ryuga's temper ruining their plan, Evolto approached Rogue as he kicked the stand, which projected a hologram of the Pandora Box. Evolto commended the Kamen Riders for their ingenuity as Rogue turned to Evolto, calling him by his host's name. Secretly scheming to obtain the data on Katsuragi's Sclash Driver system, Evolto coaxed Gentoku into laying out a trap for Sento and Ryuga to bring the Pandora Box to the hospital Taizan was recuperating. After having his father contact Sento, Gentoku informed Evolto the riders took the bait. Evolto asked Gentoku if this atones for his betrayal, but Gentoku told him it all depends on what happens tomorrow, which Evolto replied with his comedic tendency.

While Sento and Ryuga walked into the trap, Evolto snucked into nascita and copied the schematics for the Sclash Driver on a USB driver, commending Sento for completing it until he heard Misora call him. Looking at her, he pulled out the drive with the copy data as she asked him where he's been, which he replied with his comedic tendency that he was on a spontaneous trip until Misora demanded a straight answer. She asked him to tell her what he did, no matter how bad it may seem. Pretending to be serious, Evolto admitted that his part-time job was a lie, and he countered with another lie by showing her a case of coffee beans and telling her he's been cultivating his own. Misora bought the lie and scolded Evolto as he pointed out his obsessive trait about trying to make good coffee. Misora admitted she's been worried for him, and Evolto stated he's going to be even more busy from now on, leaving no time for him to see her and asked her to say hi for him to Sento and Ryuga. As he prepared to leave, Misora looked back on her times with Evolto, saying she liked his lame jokes and obnoxious laughing and will treasure them no matter what happens before thanking him. Evolto joked around with Misora's formality and left, completely unaware that she figured out he's working with Faust.

After Build and Cross-Z escaped with the Pandora Box, Gentoku barged into the Touto government's office where Evolto waited for him, demanding to know why he wasn't at the hospital during the trap. Evolto, being amusing, presented him the coffee beans, stating he had to do important business, angering Gentoku enough to make him grab Evolto's beans and tossed them on the ground before seizing Evolto's jacket and demanded if he tricked him. Evolto told him in shock and fear to let go of his jacket, which was his favorite. Rising from the table, Evolto told Gentoku not to worry as Evolto brush his jacket, assuring Gentoku he'll follow up and decided to reveal Sento's origin to Gentoku. Evolto revealed that Sento is actually Katsuragi, and confirmed it by showcasing to Gentoku his face-changing ability on a guard. He also explained everything about how Katsuragi became Sento and his amnesia. After Gentoku's cover was exposed to his father Taizan and the Pandora Box safely secured in the Touto capital, Evolto decided his alliance with Touto has served his purpose. The next day as Taizan made plans before preparing for his seven PM meeting with the other prime ministers, Evolto, as Blood Stalk, injected him with a poison, leaving Taizan comatose. Stalk decided to cover up for Gentoku, keeping his identity as Night Rogue secret as he saw Gentoku taking part of his next scheme. Within the next few days, Stalk stood in Prime Minister Tajimi's office while she viewed Hokuto's invasion into Touto from one of Hokuto's Guardians, having form an alliance with Hokuto in the second phase of his overall scheme. Stalk chuckled as Tajimi declared war on Touto for the Pandora Box.

Days into the Touto-Hokuto war, Evolto, as Blood Stalk, watched from the shadows as Tajimi attempted to manipulate Mido into siding with her after Hokuto has taken the Pandora Box from Touto, all a front for her to keep the box for herself while she was unaware of Mido biding his time to take Hokuto. After both Prime Ministers formed an "alliance", Stalk approached Tajimi from behind, stating she has no intentions to join forces with Seito, which she admitted joyfully and added with the box she could control the entire world. Stalk shuddered as he called Tajimi a scary lady before he told her Kamen Rider Grease and the Hokuto Three Crows should be retrieving the Touto bottles right now. At night after Kamen Rider Grease made contact with Kamen Riders Build and the new Cross-Z Charge, Evolto, as Isurugi, contacted Sento from the Faust Hokuto branch lair. Sento asked him what he wanted, which Evolto commented as straight to the point for a cool guy, and Sento admitted he wanted to talk to him. Evolto apologized for copying the Sclash Driver data, which Sento added Evolto would need someone with the right skills to build the belt.

After Sento asked who built it, Evolto revealed the driver was constructed by Namba Heavy Industries before he mentioned he learned of Ryuga's usage of the same driver, which Sento stated he won't let Ryuga use it anymore as the Sclashjelly subjects the user a direct exposure to the Nebula gas, giving off a side-effect of lusting for war and combat, almost like a person's personality being altered by the Pandora Box's light. Despite this, Evolto stated without the Sclash Driver Sento and Ryuga can't defeat Grease and the Hard Smash, but Sento stated he'll bare the driver's effects so he can protect Ryuga, Misora and Sawa. Sento then asked Evolto if he defected to Hokuto, which Evolot shrugged in agreement and asssured he won't tell Hokuto about the lab in nascita as it would sully his game. As Sento asked what his true motives are, Evolto reminded him all he wants is to see Sento and Ryuga grow as Kamen Riders, and he looks forward to it before hanging up.

The Forbidden Item & Siding with Seito
1="You're free not to enter the proxy fight. But if you don't, who do you think will enter instead of you? Banjo. Banjo fells like it's his fault for what happened to you. So if you don't do, he'll probably volunteer for the job. But he can't defeat Grease as he is right now, IF that happens, all of Touto will turn on Cross-Z. You have to fight. You know that. That's why you came here hoping for something to help you!"

- Evolto, as "Soichi", attempting to encourage Sento to fight in the Touto-Hokuto proxy fight.

2="Stand up. Raise your Hazard Level and find the best attacks for the Bottles by fighting me. If you raise your level, you might even be able to control the Hazard Trigger. Why are you hesitating?! Don't you have something to protect? Weren't you going to fight for the justice you believe in?! Or was it all a lie?!"

- Stalk encouraging a horrified Sento to fight.

As Grease and Cross-Z Charge launched their attacks at one another, Evolto, as Blood Stalk, appeared in a red-flame energy, cancelling their attacks before they connected. Intervening on the fight between Build, Cross-Z Charge, Grease and the three Hard Smash outside of the Touto capital, Stalk commended them for their battle while the Castle Hard Smash asked him why he arrived during the fight. Stalk told him that he decided to read their Hazard Levels individually to compare them. Moving swiftly before either Rider or Smash can react, Stalk touched Cross-Z Charge, Build RabbitTank Sparkling, Grease, Stag, Owl and Castle before heading back to the center to announce their Levels: Castle's being 3.7, Owl at 3.6, Stag at 3.7, Grease at 4.2, Build at 3.9, and Cross-Z Charge at 4.0. After announcing their strengths, Stalk scolded Build for letting Cross-Z Charge's level rise quicker than his own as it will now be impossible to stop him. Deciding that's enough for the day, Stalk told Grease and the Hard Smash to return to Hokuto with him, per Tajimi's orders. Stalk teleported while Grease used the Keshigomu bottle to disappear with the Hard Smash.

Back at the Hokuto Faust lair, Stalk sat between Tajimi and Kazumi as she told him why she summoned him back: his failure for not retrieving the Pandora Box and Touto's bottles quickly. Kazumi cursed as he brushed off her claim and replied he's stronger than Build and Cross-Z due to his higher Hazard Level, but Stalk stated it's temporary as Ryuga grows in strength quicker than anyone else, and in time the table will turn against Kazumi. Kazumi suggested to enhance his body once more, but Stalk assured him it won't raise his Hazard Level quickly and instead, stated the Three Crows can level up with a new item he recovered: the Hazard Trigger. Showing it to Kazumi and Tajimi, Stalk told them it can enhance their Hazard Level instantly, making them stronger than before. Sitting beside Kazumi, he mentioned a trade-off: if they're defeated, they'll die, which forced Kazumi to decline Stalk's offer. Mentioning it will be a pain to defeat Ryuga once his level's higher than Kazumi's, Tajimi added if Kazumi fails to retrieve the Touto bottles, she'll fire him before Kazumi left, telling her adamantly that he'll retrieve the box and the bottles before that. As Stalk turned to Tajimi before she called out Akaba, Aoba and Kiba, Stalk shook the trigger as Tajimi asked them what they want to do since Kazumi doesn't want them to undergo the enhancement.

Agreeing to undergo the procedure, Stalk set up the Hazard Trigger to the container and activated it with Kiba going first. While watching Kiba being painfully enhanced, Akaba told Stalk that Kazumi paid for his, Kiba's, and Aoba's families out of his own pocket back at his farm and worked hard to provide for them until the Skywall left the farm's land barren. Patting Akaba on the shoulder as an act of compassion, Stalk stated that was why Kazumi volunteered to become Kamen Rider Grease as Akaba thanked him for turning him, Kiba and Aoba into Hard Smash to help Kazumi. As Stalk told him not to worry about it, Kiba's enhancement was complete as Faust scientists helped him out of the vat and into bed before Aoba went in for his turn, hearing both Aoba and Kiba stating they can help Kazumi with their new power. Turning on the vat, Stalk turned away as Aoba underwent his enhancement, chuckling as his proposal to raise the Three Crows' Hazard Level was the next stage of his plan for Sento.

Outside the Touto garbage plant, Stalk watched from the shadows as the Three Crows, renamed themselves as Hazard Smash, overwhelm Build RabbitTank Sparkling until he was forced out of his transformation and lose the Harinezumi, Shoubousha, Soujiki and Phoenix bottles while Cross-Z Charge engaged Grease. As Grease left with the Hazard Smash via Helicopter bottle with Cross-Z Charge pursuing them with the Taka bottle, Stalk unveiled himself to Sento, telling Sento he figured the Hazard Smash would end up going out of control and the only way he could defeat them was with the Hazard Trigger, the forbidden item Sento created as Katsuragi, all a lure to bait Sento into using it.

Tossing the device to Sento, Stalk reverts back into his host's form, assuring Sento by placing the Hazard Trigger into the Build Driver will grant Sento even greater power than he had before, even great enough to stop Ryuga as he succumbs to his Sclash Driver's side effect. As Sento surmised there's a trade-off for the Hazard Trigger since it's coined the "forbidden item", Evolto revealed that prolonged usage of the trigger would cause the user to lose oneself, leaving it vague for Sento to learn that prolonged usage would cause the user to blackout and become berserk, attacking everyone in its path. Evolto also added the Three Crows would die once they're defeated in their Hazard Smash forms due to the trigger's energy being directly injected in their bodies. Moving to Sento's side, Evolto stated the trigger really is a forbidden item as Sento asked why he's giving it to him. Evolto, being vague once more, told him it's part of his plan to keep Sento alive and he's the only one who can stop Rygua, all so that both riders can encourage each other to grow stronger as Ryuga's a born fighter and Sento's strength comes from his knowledge and usage of science. Sento then asked why that's connected to his long-term goal, but Evolto decided to not go further and left.

After learning of Aoba's death at the hands of Sento under the influence of the Hazard Trigger and his refusal of the Hokuto-Touto proxy fight for the Pandora Box a week after, Evolto, as Isurugi, waited in a park until Sento approached him. After asking Sento of his refusal, Evolto laughed, riling a horrified Sento to ask him what's so funny. Evolto told Sento due to his stubbornness he hasn't learned that both he and Aoba were no longer human once the Nebula gas has been injected in their bodies, so he called Sento's remorse as whining over a destroyed weapon, something inevitable once war broke out. Walking towards Sento, Evolto pointed out that Sento believed he could get through the war without casualties, scoffing at the notion of Sento's optimism having limits. He then told Sento that if he doesn't participate in the fight, Ryuga will in his place due to his guilt of Sento utilizing the Hazard Trigger, even though his strength is nowhere near Grease's, which will solidify Hokuto's shot at victory and all of Touto will shun Ryuga.

Turning to Sento, who has become even more conflicted, Evolto told him he has to fight and he knew that deep down, which is why he came to see "Isurugi". With his conflict lashing against reason, Sento attempted to punch Evolto, who dodged and punched Sento in the gut before he fell down. Breaking down, Sento asked what he should do, and Evolto told him to defeat Grease but Sento whispered he can't do it. Seeing through him, Evolto pointed out Sento's fear of going berserk from the Hazard Trigger, and pointed out there's a way to win as he grabbed the satchel he brought with him. As he placed the satchel on the ground, Evolto told Sento the greatest feature of the Build Driver is the hidden abilities that can't be measured with Hazard Levels, and presented the contents in the case: a Hokuto panel with ten of Hokuto's bottles and a Seito panel with ten of Seito's bottles. Evolto told Sento he'll let him borrow them so he can train with them in the week before the fight before transforming into Blood Stalk. As he told Sento to stand up to start his training, which can help Sento control the Hazard Trigger longer before the side-effect kicks in, Evolto was irritated that Sento didn't budge. He then scolded Sento for all of his talks about justice and fighting to protect that which he holds dear and asked if it was all a lie, which forced Sento to finally accept as he took the Phoenix and Soujiki bottles, transforming into Build PhoenixSoujiki Trial Form.

Still horrified, Build engaged Stalk with fire attacks, which Stalk dodged and deflected before he pointed out what's the Long Range Cleaner for if Build won't use it. Kicking him back, Stalk summoned his Transteam Gun and fired as Build replace the Phoenix bottle with the Rose bottle and transformed into Build RoseSoujiki, sucking up the gun's shots with the Long Range Cleaner and attacking with a vine from the Ibalash Arm until Stalk saw an opening and shot Build. Stalk then told Build the Trial Forms won't work, forcing Build to switch the Soujiki bottle with the Helicopter bottle and transform into Build RoseCopter Best Match. Build runs and lash out on Stalk with the Batrotor Blade, but Stalk countered each strike with his Steam Blade, commenting on how much Build loves red and green since he transform into those forms with those colors frequently. Build and Stalk matched each strike until Build gained the advantage and performed a Vortex Finish Rider slash, hitting Stalk directly. Joy flowing through him, Stalk commented on the Best Match's abilities defying expectations before telling Build to keep going, which Build replied by transforming into TurtleWatch Best Match.

As the week passed, Evolto, as Blood Stalk, stood beside Tajimi in the Hokuto capital as they watched the proxy fight begin through the television. Stalk paid no attention as Tajimi said to herself she's counting on Grease to win. As they watched Build and Grease trade blows, Stalk saw Tajimi become shocked when Build transformed into RoseCopter and ToraUFO Best Match forms, and as Grease turned to the camera, Stalk proudly admitted to lending Build half of both Seito's and Hokuto's bottles. Stalk then added if Grease wins, then the bottles will be returned to them. As Build overwhelmed Grease with the KujiraJet and KirinCyclone Best Match forms, Stalk and Tajimi saw Grease riled up and turned the table on Build, which Tajimi complimented on before Stalk asked her what Hokuto's army doing; Tajimi revealed she had them march toward Touto and waited for her word to attack if Grease loses, which was Stalk's suggestion.

As the fight progressed with Grease in lead, Build pulls out the Hazard Trigger and transforms into RabbitTank Hazard, confirming Stalk's suspicion of Sento utilizing the device in the proxy fight. As Stalk also expected, Build was in complete control over the Hazard form until he lost consciousness and went berserk as night fell and defeated Grease as Build HawkGatling Hazard, felling him with a Hazard Finish Rider shooting, signalling Touto as the victor. Stalk made no motion while Tajimi was shocked at the outcome, and then angered after Cross-Z Charge stopped Build from killing Kazumi. Tajimi deemed she will have the Pandora Box and attempted to give the word to attack Touto until Stalk took her phone, stating that's against the rules. As Tajimi questioned why he would stop her as the attack was his idea, a platoon of Seito Guardians stormed in the briefing room, surrounding Tajimi. Stalk then revealed that his suggestion was just to place Hokuto's army away from Hokuto, allowing Seito to invade and seize control, and he told Tajimi all she can do is surrender. As Tajimi asked why he betrayed her, Stalk told her not to get the wrong idea: he was never on her side as two Seito Guardians seized her by the arms. As she struggles to break free, Stalk noticed a purple and black Kamen Rider with cracks attributes entered the room, dragging the upper portion of a Hokuto Guardian by his right. Stalk commended the rider on his performance, and introduce him as Seito's Kamen Rider: Kamen Rider Rogue.

After the 3-on-3 Proxy Battle ended with victory for Touto, Blood Stalk was summoned by Namba to kill Seito's Prime Minister Masakuni Mido when he refused to dishonor his promise to relinquish his claim to the Fullbottles and the Pandora Box. Blood Stalk then used his power to modify Namba's face into that of the late Prime Minister, allowing him to personally take control of Seito and launch his own invasion of Touto using the full arsenal of Namba Heavy Industries Ltd..

War for the Pandora Box
After the Seito Guardians escorted Tajimi to a secured Seito location, Blood Stalk sat in a chair with Tajimi's cell phone and the second Hokuto Pandora Panel, waiting for Kazumi to call after word of Seito seizing Hokuto reached Touto. Answering the phone, Stalk confirmed to Kazumi's question, who thought Tajimi was still in her office until he realized Stalk has her phone, about Seito seizing Hokuto. As Kazumi surmised for him being in cahoots with Seito, Stalk chose to obliged him and said Seito will take all of Hokuto, including Kazumi, Akaba, Kiba, and the late Aoba's families and friends, but Kazumi warned him Seito won't get away with this. Stalk then told Kazumi that depends on his attitude and told him to wait for Mido's announcement on what will happen next before hanging up. Stalk turns to Kamen Rider Rogue, chuckling as the third phase of his plan is set.

After Sento, Ryuga, Kazumi and Akaba learned of Kamen Rider Rogue's identity, the exiled Gentoku Himuro, Sento headed back to the abandoned warehouse where he killed Aoba, laying a blue and yellow flowers on the spot and praying until Stalk approached him, surmising that Sento has accepted the burden of their deaths. As Sento asked what he wants, Stalk told him he's taking back the bottles he lended to Sento for the Touto-Hokuto proxy fight, but Sento declined and vowed to never let Stalk have his way anymore. Stalk told Sento if he doesn't give them to him, Rogue with take them by force, commenting on how both Sento and Gentoku are similar due to their reasons for fighting, but their resolves are different as Gentoku has nothing to lose now but Sento still cares, which Stalk sees as a restraint. As Sento told him not to presume anything, Stalk demanded the bottles once more, but Sento rejected the request as he transformed into Build RabbitTank. Leading the fight inside the warehouse, Build transformed into RabbitTank Sparkling, but Stalk deciced to fight with more of his strength, faring well against Build as he told he can no longer win now unless he uses the Hazard Trigger. Spotting his next move, Build leaped forward to attack, but Stalk evaded it with his accelerated speed and countered with a more powerful kick, not only sending Build to the floor but to force him to drop the Hachi, Sensuikan, Spider, Reizoko, Phoenix and Kabutomushi Fullbottles. As Stalk placed them in one of Seito's Pandora Panels, he told Build to hand over all of Touto's bottles as well so he can open the Pandora Box quickly, but Build told Stalk he won't as he inserted the Hazard Trigger in the Build Driver and transformed into KaizokuRessya Hazard.

Stalk became satisfied by Build's decision as he attacks with the Kaizoku Hassyar, taking every blow as he told Build to attack with even more force. As Build stated he can still go on, the Trigger's effect kicked in, stripping Build of his consciousness and dropped his weapon, going berserk and activated the Trigger's Overflow attack as he laid a series of punches at Stalk while he counted Build's rising Hazard Level to 4.4, stating this is the power of the Hazard Trigger. As Build raised him while still punching him, Stalk told him to keep going beyond his limits as the berserk Build punched Stalk hard enough to send him flying through the wall and out of the warehouse. Slowly rising, Stalk yelled at Build to go beyond his expectations and to keep pushing beyond his limits, as he questioned if Build can reach the level he wants the rider at. As Stalk prepared to fight the advancing berserk Build again, Kamen Rider Grease arrived and performed a Scrap Finish Rider kick, forcing Build out of his transformation. Grease then turned to Stalk, telling him he wants in on the fun as Sento regained consciousness, but Stalk became annoyed by his interference and pulled out the panel with the six bottles, stating he'll let Rogue take the other bottles back before pulling out his Transteam Gun and typhoportated.

The next day, Evolto, as Isurugi, received a call from Sento and met him near a lake, wondering why he called him. Sento told him he this meeting was about Misora, which Isurugi told him he knew that she managed to open a hole in the Sky Wall, but he suspects that the Martian queen Vernage was still alive and is somehow connected with Misora. Sento asked about Misora's bangle, which Isrugi revealed that he found it on Mars and brought it back with the Pandora Box, and that it wouldn't come off after it was placed on her wrist. As Sento asked what the world "Evolto" meant, Isurugi pretended to play dumb and not know what it meant, then switched the subject by pointing out that he'd never thought Misora could be a wild card. Interpreting that as a threat, Sento warned Isurugi not to harm Misora, but Isurugi told him he wouldn't do anything to his own daughter, even though Sento spots no concern in Isurugi's face. Chuckling, Isurugi admitted he won't ever face someone who was the power to manipulate the SKy Wall, and that for now he'll focus on retaking the Pandora Box, but Sento assured him it won't be possible. Deciding to elevate his plan, Isurugi told Sento that Seito has all of Touto's intel and mention the Namba Children, orphans who were taken in by Juzaburo Namba himself and trained to become scientists, soldiers and spies with utmost loyalty to Namba. He then told Sento that the Washio brothers, the wielders of the modified Kaiser System, and Utsumi are Namba Children as Sento surmised there's one Namba Children who's a spy feeding vital intelligence to Seito as Isurugi took his leave.

From afar, Evolto watched a proxy fight between Seito and Touto for the Pandora Box and all the Fullbottles, in which Mido proposed to share the Martian relic among the three regions, call back Seito's army and restore Hokuto, and in the end Seito lost due to Seito's new power-up: the Fullfull RabbitTank bottle. Evolto, as Blood Stalk, stood outside the viewing room where Mido, Namba and Utsumi were in, waiting for Namba to call him in as he expected Namba to take matter in his own hands as he opened the door. Walking in the room, Stalk asked if it's his turn as he turn toward a frightened Mido. As Mido demanded to know what's going on, Stalk shoved him down on the couch and shot his tendril in Mido's chest, injecting enough poison to kill Mido. As Mido asked why, Stalk simply stated his purpose has run its course, leading to Mido asking who will lead Seito with him dead as the poison disintegrates his body. To his horror, Namba said he will take Mido's position as Prime Minister as Mido attempted to seized Namba but the poison takes full effect, forcing Mido to grab the Seito flag as he falls to the floor, his body completely disintegrated, horrifying Utsumi. Stalk obliged Namba's command by using his face alteration power on Namba, turning him into Mido before taking his leave, now shifting to the next phase of his plan.

Residing in a secret lair with the Pandora Box resting on a stand, Stalk pulled out a Touto Pandora Panel with the Gorilla, Diamond, Lion, Soujiki, Ninjya, Comic, Harinezumi and Syoubosya Fullbottles inserted, followed by Stalk inserting the Octopus and Light bottles as he followed the orchestra theme being played by Namba, via Mido disguise, while his Hard Guardians overtake Touto. With the Light bottle inserted, Stalk placed the panel in a slot similar to the one from the first Faust lair until the panel glowed green before attached itself to one of the Pandora Box's side, which affected the whole lair and changed it to a bigger one with columns. While dancing, Stalk used the box to alter the Sky Wall, changing the solid wall to one with spaces between them, and a large red light began to glow from the box itself all the way to the center of the converged point that divides Japan into Touto, Hokuto and Seito. From that convergent point, a tower's base erected while destroying everything in its path and hurting all who lived in close proximity.

Heading to the surface, Stalk arrived where Build RabbitRabbit, Cross-Z Charge and Grease are engaged against newly built Guardians, which Stalk informed them they're the latest innovation of Guardians from Namba Heavy Industries called Hard Guardians. Watching two Hard Guardians seize Grease, Stalk formed his Steam Rifle and shot Grease twice, forcing him to drop the remaining four Hokuto bottles, which Stalk took as he stated the Pandora Tower will be completed. Stalk then inserted the bottles in one of the Hokuto Pandora Panel, which glowed blue as Stalk attached it to the Pandora Box, causing the tower to rise taller than the segmented Sky Wall. Stalk praised the tower as he told Build, now in TankTank, Cross-Z Charge and Grease that the tower is built by the Pandora Box's power, and with it's completion the Earth will be destroyed like Mars. As the Hard Guardians withdrew, Stalk proclaimed their assault as a declaration of war, and the fight coming will be much worse before taking his leave.

Returning to Seito's capital, Stalk reverted Namba's face back to normal as Namba complemented his original face being the best for him, no matter how young he looks due to Stalk's power. As Namba expressed his amazement of the Pandora Tower's creation from adding two Pandora panels, Stalk assured him the tower will grow as the remaining four panels are attached, and added that they have 27 Fullbottles in their possession. Despite this, Namba stated he doesn't trust Stalk while also adding Stalk's power is incredible before ordering Stalk to collect the remaining 33 bottles. Annoyed, Stalk chose to obey in order to keep Namba satisfied until his usefulness run its course.

The next day, Stalk typhoportated with Engine Bro's, Remocon Bro's, and two Hard Guardians to intercept Kazumi and Ryuga on the road connecting Touto and Hokuto, informing his party to do a good job today. Seeing the imminent danger, Kazumi and Ryuga transformed into Kamen Riders Cross-Z Charge and Grease, engaging the Bro's and the Guardians. While Grease takes on the Washio brothers, Cross-Z Charge engaged Stalk, who commended Cross-Z Charge's increased strength, which Cross-Z Charge told him not to get cocky as his Hazard Level is higher than Stalk's. Stalk admitted it's true, but he can compensate with his hidden power: the ability to generate crimson flames. He shoots Cross-Z Charge in the face with a crimson fireball, sending the rider down on the dirt. Rising, Cross-Z Charge realized the crimson flames is another ability Stalk obtained on Mars as the Wahsio brothers strike Grease with two energy cogwheels, sending him flying next to Cross-Z Charge.

Dissatisfied with the quick defeat, Stalk told them to hand over the remaining Fullbottles until Sento approached from behind. Inserting the FullFull RabbitTank bottle in the Build Driver with the Hazard Trigger, Sento transformed into Build RabbitRabbit before engaging Stalk and the two Hard Guardians. While Grease decided to join Build in fighting against Seito to end the war and engaged the Wahsio brothers, with Rai handing his Gear Engine to Fu so he can transform into Hell Bro's, Stalk engaged Cross-Z Charge once more. As Cross-Z Charge prepared to execute a Scrap Break Rider thrust, Rai shouted eveyone to stop as he dragged an unconscious Misora, who was nearby prepared to ask Grease to help Sento and Ryuga end the war. All three riders were shocked as Rai demanded the remaining Fullbottles, but Misora woke up with her eyes glowing green, which shocked Stalk and then everyone as Misora conjured a golden aura, sending Rai flying in a wheat patch. Stalk then realized that Vernage has possessed Misora.

As all the Riders and Hell Bro's were stunned by this revelation, Stalk was irritated that Vernage was still alive, and aimed his Transteam Gun at Misora's body. Sensing the danger, Vernage cast a shockwave powerful enough to send Stalk flying and cancelling his transformation. Rolling to his hand and knees, Evolto, as Isurugi, noted Verange's strength and generated crimson flames on his Transteam Gun, firing it at Vernage until Cross-Z Charge jumped in the shot's path. The blast destroyed Ryuga's Sclash Driver and incinerated the Dragon Sclashjelly into a smoldering crisp as Ryuga dropped to his knees. Before Evolto's eyes, Vernage teleported herself, Ryuga, Build and Grease away, but Evolto chuckled and deemed Vernage's presence will make the fight from here on more interesting. Returning to the Seito capital at sunset, Evolto revealed to Namba and Utsumi of Vernage, which Namba found impossible, but Evolto understands his skepticism as this would fall under a "what you see with your own eyes" scenario while he stacked sugar cubes. Utsumi expressed his concern as Vernage is a powerful threat to their plan, but Evolto assured him not to worry as Vernage's power will fade away and she knows it.

With night emerging after they returned to Pandora Tower, Evolto and Gentoku leaned on two columns as Utsumi ordered the Washio brothers to protect the tower at all costs. As the Wahsio brothers left with their new roles, Gentoku asked Utsumi why Seito invaded Touto, but Utsumi chose not to answer him and to do what he said. As Gentoku told Utsumi he's no lap dog, Evolto reminded him of the chip in Gentoku's body, meaning he has to do what he's told. In the morning as Kamen Riders Build, Cross-Z and Grease engage the Hard Guardians in front of the Pandora Tower, Evolto walked around, saying it's time to get serious, as he attempts to transform with his Transteam Gun, his left arm seized the right, and to Evolto's surprise, the real Soichi Isurugi emerged briefly, asking Evolto what he's trying to do.

Regaining control, Evolto told him not to do that again and to keep silent and watch as he transformed into Blood Stalk with crimson flames coursing all over his body. While observing the three Riders destroy the Hard Guardians, they attempted to burst through the Pandora Tower until Stalk used the Pandora Box's power to open a doorway that let the three Riders in, to their surprise. Stalk then shifted the room the three Riders were in to let the Washio brothers and two Hard Guardians in before the brothers transformed into Engine Bro's and Remocon Bro's. As they fight, Stalk altered the room with lasers, sections of the wall and floor popping out and traps, which overwhelmed Cross-Z, Build TankTank and Grease. As Build noted the alteration, Stalk used the box's power to broadcast his voice and view the fight, informing them he alone can alter the tower with the Pandora Box, questioning if they can escape as he altered the room again with more traps.

During the fight, Stalk noticed Cross-Z's power rising as he easily defeated Engine Bro's, and decided to transport the Hard Guardians, Hell Bro's, Build TankTank, Cross-Z and Grease to a beach, followed by Gentoku. After Build easily defeated Hell Bro's and Rogue, which latter allowed as he informed Build of Namba's usurpation of Mido's position, with a FullFull Match Break Rider slash, Stalk opened a portal back in the Pandora Tower, allowing Sento, Kazumi and a depressed Ryuga to enter. As they made their way deep in the power, they approached a wall that opened, revealing Stalk sitting on the floor in front of the stand with the Pandora Box. Satisfied they made it, Stalk went straight to the point and gestured they're here for the Pandora Box, and then he said he wants the remaining Fullbottles the Riders have, and since they're at an impasse he summoned two strange Smash Hazard: Octopus and Press. After they transformed, Build RabbitRabbit and Grease engaged the Smash while Cross-Z stood back as anger swelled within him. Build and Grease's attacks on the Smash have no effect, which Stalk revealed they are clones made to feel nothing, and as he rose he told Cross-Z they should start fighting as well as a crimson aura emerged briefly from Stalk's body.

"Finally, the vessel is complete. Now I just need to find the ultimate driver, and everything will be in place."

- A defeated Blood Stalk now satisfied with Cross-Z's new power.

As Cross-Z and Stalk traded powerful blows, Stalk told him the Transteam System doesn't impede his strength until he began to overpower Cross-Z. While holding Cross-Z's arm, Stalk informed Build that the Clone Smash have no nerves, meaning they will continue to fight until they die, and Cross-Z asked Stalk what he's after as he killed Kasumi to make Cross-Z stronger, which Stalk became annoyed as he deduced Rogue told him and chose not to answer Cross-Z, which angered him even more. Catching Cross-Z's fist, Stalk decided to come clean and told him he did and that he wanted Cross-Z's strength, but due to Cross-Z's current strength level it wasn't enough to indulge Stalk as he tossed Cross-Z aside and fired a beam from the Pandora Box at Cross-Z, which infuriated Grease enough to engage Stalk. Deflecting Grease's blows, Stalk told him his strength isn't enough either as he fired a crimson blaze, sending Grease in air until Stalk used the box's power to cause part of left wall to slam Grease to the right hard, cancelling his transformation. As Build realized he can control the box, Stalk fired a beam from the box that ensnared Cross-Z in a red energy box that imploded, cancelling Cross-Z's transformation.

Stalk asked the fallen Ryuga if that's all the power he could muster before firing another beam from the Pandora Box, but Build TankTank shielded Ryuga and took the front of the blast, knocking Sento out of his transformation as he fell on his knees. Stalk seized Sento by his hoodie before he fell face down on the dirt and straighten him on his knees, asking Sento if he wanted to die now before kneeing him in the face. Seizing Sento by the hoodie once more, Stalk chose to oblige Sento and dragged him to the other side of the room, then held him by his collar as he asked Ryuga if he's just going to stand back and watch someone close to him die again, which was a ploy to get Ryuga to raise his strength again. Hoisting Sento up, Stalk turned to see Ryuga standing once more and his eyes glowing red, an indicator of Evolto's genes coursing through Ryuga thirsting for more power. Happy, Stalk dropped Sento and headed to the Pandora Box, telling Ryuga to keep going as he fired another red beam from the box, but this beam empowered Ryuga, allowing him to turn the charred remains of the Dragon Sclashjelly into the Dragon Magma Fullbottle, then at Sento's request, inserted the new bottle into the new knuckle weapon before inserting in his Build Driver, like Cross-Z Dragon, and transformed into a new form: Kamen Rider Cross-Z Magma.

At the sight of Cross-Z Magma, Stalk motioned the Clone Smash to fight Cross-Z Magma, who easily destroyed them before engaging Stalk. Beginning to fell overpowered, Stalk told Cross-Z Magma to keep going, which he did with a constant series of magma-powered assaults before performing a Volcanic Attack Rider kick, which destroyed Stalk's energy cobra as the kick connected, weakening Stalk as he rolled on the ground. Cross-Z Magma then painfully walked to the box as his new power began to burn him, but as Stalk stated he won't let them take it, Cross-Z Magma unknowingly triggered the Martian relic's power, causing two pillars to form from both walls to entrap Stalk and the left wall created an exit out of the Pandora Tower. While Cross-Z Magma grabbed Kazumi, Sento attempted to leave, but turned to see a defeated Stalk on his knees, saying that now the vessel is complete, he must locate the ultimate driver until Cross-Z Magma told Sento to hurry, leaving Stalk to stare at the ceiling.

Reunited with the Evol-Driver & Becoming Evol
1="I...I finally have it again!"

- Evolto rejoicing in reuniting with the Evol-Driver

2="Evol Phase 1."

- Evolto transformed into Evol Cobra Form.

The next day at the Seito capital, Evolto, as Blood Stalk, sat on a couch observing a crimson cobra-style bottle as Namba, in his Mido disguise, just ended a hologram conversation with Taizan, stating they will take back Pandora Box by force. Namba then told Stalk to retrieve the box, but Stalk told him he will retrieve it in due time as the ultimate driver is the top priority. As Namba asked about this driver, Stalk told him it's the only device capable of utilizing the Pandora Box's full power before fibbing about it being the ultimate weapon Namba has been seeking. Namba then asked if Stalk can retrieve the driver, which he told Namba it won't be easy due to its nature, which other would classify as a dangerous tool. Stalk, however, assured Namba he will find it before taking his leave.

Stalk sent a squad of Hard Guardians, led by Engine and Remocon Bro's, to a bridge as a distraction for Kamen Riders Grease and Build, while he and Kamen Rider Rogue lead an assault on the Touto capital. While easily defeating Touto Guardians, Stalk spotted Kamen Rider Cross-Z, who was conflicted after learning of his alien origin, and engaged him as he told Rogue to proceed on in the capital. Trading blows before allowing Cross-Z to pummel him aggressively, Stalk noted how strong he has become without utilizing his Cross-Z Magma form and called him a monster. Cross-Z told him to shut up and he's human, which Stalk realized Sento had Sawa retrieved the file on Banjo's true origin, which shocked Cross-Z, allowing Stalk to grab his arm as he told the rider he knows everything about him before shooting him in the back with his Transteam Gun, sending Cross-Z flying and cancelling his transformation.

Walking to a defeated Ryuga, Stalk told him they both have the same power, the very power to destroy the world, which confused Ryuga. Stalk then elaborated to make it more clearer for Ryuga by stating he came for one reason, which wasn't to help Sento or to protect Touto: to fight, the only thing that can satisfy Ryuga, and that avarice for conflict alone will eventually lead to destruction. Ryuga attempts to deny it, but Stalk told him bluntly to accept his alien heritage before kicking him down a set of stairs. As Stalk sat down, he watched Sento, who overheard everything, approaching and told Ryuga to stay back as he prepares to activate his FullFull RabbitTank bottle. Ryuga stopped him and shoved him as he rose, stating he is a Kamen Rider, and even if he's an alien he's not the same as Stalk. Activating his Cross-Z Magma Knuckle, Ryuga vowed to use his power to protect and bring love and peace before transforming into Cross-Z Magma. Sensing Cross-Z Magma's new resolve, Stalk stood up and engaged one another, trading blows until Cross-Z Magma's attacks begin to overwhelm Stalk. Driving Stalk in a corner, Cross-Z Magma unleashed a Volcanic Attack Rider kick, followed by a Volcanic Knuckle Rider punch on Stalk, defeating him once more. In pain, Stalk congratulated the Kamen Rider for accepting his heritage and that he can't deny his fate before typhoportating away, laughing as his plan succeeded with Rogue abducting Taizan.

The next day, Evolto called Sento from the Pandora Tower, joking lightheartedly at Touto being in chaos with its Prime Minister kidnapped. After Sento told him it was his doing, Evolto proposed a deal: in exchange for returning Taizan, he wants the ultimate driver, called the Evol-Driver, turned over to him. As Sento became confused, Evolto revealed the Evol-Driver was the basis for the Build Driver's development and invented by Sento's father, Shinobu. Evolto also revealed that Sento learned of the driver's existence as Katsuragi and hid it before losing his memory. He told Sento to find it and bring it in one day at a wharf and Taizan will die if he shows up late before hanging up.

That night at an abandoned factory where Taizan was kept prisoner, Evolto, as Stalk, watched from atop a building as Gentoku broke his father out and attempted to flee, only to run into Utsumi and a Strong Clone Smash before Taizan shoved Utsumi aside, allowing Gentoku to throw the remote to his chip from Utsumi and transformed into Kamen Rider Rogue. After Rogue destroyed the Clone Smash, Stalk pulled out a second remote and activated it, shocking Rogue and cancelling his transformation. Stalk told Gentoku now he understands why he wants to reunite Japan, and revealed to Taizan that the Pandora Box's light in Gentoku is now due to his increased Hazard Level to become a Kamen Rider before jumping down. Stalk also pointed out Gentoku put up this facade to keep his father in power to reunite the country, realizing he cannot do it himself as Utsumi seized Taizan. Stalk turned to Gentoku, telling him he controls his fate as he kicked him down and left with Utsumi and Taizan, unaware that Gentoku reached for the first remote.

The next at the wharf, Stalk waited inside the building with Faust Guardians, holding Taizan, and a Hard Guardian until Sento and Ryuga arrived with the reconstructed Evol-Driver. Walking in front of the Guardians and Taizan, Stalk asked Sento if he has it, which Sento showed, satisfying Stalk before telling Sento to hand it over, but Sento told him to release Taizan. Stalk told him to think it through that he has the upper hand as he can kill Taizan and Sento can't destroy the driver, which Taizan attempted to tell Sento and Ryuga to now hand over the driver, angering Stalk to punch him to the ground. With one Faust Guard standing over the Touto Prime Minsiter with its blade, Stalk told Sento to hand the driver over again, unaware that Rogue was creeping in the dark and jumped to his father, kicking the machine away and forcing Stalk back. With Rogue's Nebulasteam Gun raised at him, Stalk admitted his disappointment for Rogue's betrayal after letting him live before activating his remote, but saw that the chip didn't shock Rogue. Sento revealed that he and Rogue formed an alliance to save Taizan and that he changed the chip's signal to deactivate it, which Stalk anticipated as he tossed the remote aside. Taizan attempted to leave with the driver, but another Hard Guardian and Fuast Guardians blocked his path until Kamen Rider Grease arrived, knocking the robots away from Taizan.

After Sento and Ryuga transformed into Kamen Riders Build RabbitRabbit and Cross-Z Magma, Stalk ordered the Guardians to not let any of them to escape as all Kamen Riders engaged the robots, but Cross-Z Magma engaged Stalk. As Stalk dodged and parried Cross-Z Magma's attacks, he pushed Cross-Z Magma on a couple of wooden crates after the latter asked Stalk what he meant by them being the same. Stalk flicked the back of Cross-Z Magma's head as he told him he'll tell if he beats him. Grabbed by Cross-Z Magma and punched to the ground, Stalk attempted to rise until Cross-Z Magma performed a Volcanic Knuckle Rider punch, sending Stalk crashing hard to a wall before he fell down. Spotting Taizan leaving with the driver, Stalk became infuriated and projected crimson energy and flew up through the ceiling as an energy projection of a cobra, followed by Rogue utilizing the Phoenix Fullbottle's Charge Crush to fly.

Bursting through the building and landing in front of Taizan, Sawa and Misora, who has the Evol-Driver, Stalk turned to her, stating it's been a while since they've seen each other and asked for the driver, only to be knocked back by Rogue. Rogue told Stalk he's his opponent, which Stalk called him stubborn before they engaged one another, but Rogue overpowers Stalk and defeats him with a Crack Up Rider kick, cancelling Stalk's transformation. As Evolto rose slowly in anger, he spotted Utsumi grabbing Misora, who attempted to walk toward her father's body, and seize the Evol-Driver from her before tossing it to Evolto. Seeing the driver in his hands, Evolto became ecstatic and rejoiced in having his driver once again before placing it on, inserting two bottles, the crimson cobra bottle and a black one, and transformed into a Kamen Rider: Kamen Rider Evol Cobra, which he dubbed Evol Phase 1. Evol began walking toward Rogue with Misora, Taizan, Sawa and Utusmi marveling at the new rider, who caught Rogue's punch with no effort, telling him he's the warm-up. Tossing Rogue aside, Evol moved in hyper speed as Rogue attempted to hit him, then Evol overpowers Rogue with devastating assaults, doing critical damage to Rogue before unleashing an Evoltic Cobra Rider kick, sending Rogue bouncing off a beam and landing hard on the ground, cancelling his transformation.

Approaching an injured Gentoku, Evol generated spatial energy in his hand, telling the former member of Faust he has outlived his usefulness before firing the energy blast, but Taizan shielded his son, taking the attack from behind, killing him. Evol watched as Gentoku cradle his dying father, who told him to atone and rebuild Japan before passing on, leaving Gentoku emotionally devastated.

Possession of the Dragon & Completing the Pandora Box
1="How did you cure Sento of the poison?" "I helped out an enemy in need. Aren't I nice?"

- Evolto revealed to Sento, Kazumi and Sawa that he has possessed Ryuga.

2="Phase 2, complete."

- Evolto transformed into a new form: Evol Dragon.

Evol turned to see Sento, Ryuga and Kazumi emerge from the warehouse to see a petrified Gentoku holding Taizan's body, completely unaware that Blood Stalk is Evol. Evol walked towards the three riders, telling them if they wanted to say their goodbyes they should've arrived earlier, which they realized Evol was Stalk. Evol told them his new name and that he will acquire the true power of the Pandora Box with the Evol-Driver and the Fullbottles' equivalent, the Evolbottles. As Sento asked him if he killed Taizan, Evol admitted it but stated his true target was Gentoku. Evol then prepared himself with his Transteam Gun and fired at the riders as they transformed into Kamen Riders Build RabbitRabbit, Cross-Z Magma, and Grease.

Being forced down an alley, Evol held his own against the human riders until they began to overwhelm him, which he admitted that he's still getting use to the Evol-Driver's power. Cross-Z Magma asked him if he's still Blood Stalk and Evolto as he inserted his Dragon bottle into the Beat Closer and performed a Smash Hit Rider slash, but Evol blocked it as he told Cross-Z Magma his current strength is at two percent while lowering the dragon-style rider's weapon and attack him with his Steam Blade. Evol then fired at both Cross-Z Magma and Grease before firing multiple shots at all three riders, but Build RabbitRabbit remains standing. Evol declares he needs Build out of the picture in order to increase his strength as he fired at Build again, forcing him to drop the Shika, Sai and Dryer bottles, followed by injecting a more potent poison into Build after moving behind him at super speed. The poison settles in Build, cancelling his transformation as it begins to harm him, and Evol turns to Cross-Z and Grease, bidding them it's their end as well as he moved at super speed again, firing crimson blast from both hands at both riders' waist, cancelling their transformations. As Sawa and Misora ran to the poisoned Sento, Ryuga demanded to know what Evol did to Sento, which Evol revealed he injected the genius physicist with an extraterrestrial poison that will kill him in three days as he places the dropped bottle in one of Seito's red Pandora panel that has the Bat, Engine, Pyramid, Same, Bike, Hachi and Sensuikan bottles. Turning to see nothing happen as Misora begged Vernage to heal Sento, Evol stated the Martian Queen's power can no longer heal the inflicted and he's the only one who can heal Sento before taking his leave via typhoportation through his Transteam Gun.

Two days later, Evolto called Ryuga from nascita and asked about Sento's progress, which Ryuga scolded him that he's the reason Sento's dying. Telling Ryuga to calm down, Evolto offered a a chance to save Sento's life by coming back to Nascita with Misora. Evolto turned the lab upside down until Ryuga and Misora arrived, joking he thought they hid the Pandora Box in the lab. Ryuga loses his temper and demanded Evolto to cure Sento now, but Evolto panicked as Ryuga grabbed his jacket, forcing him to let go as he told Ryuga to accept his deal: for Sento's life, he wants the box and all the Touto Fullbottles turned to him. Ryuga declined, which Evolto asked him if he's okay with Sento dying, and there's no other option. Misora then told Evolto, with anger, that it's unforgivable for using her father's body and demanded the alien to give him back, which triggered Vernage's power. Evolto grabbed Misora's arm as Vernage's power created a strong gust around the lab, forcing Ryuga to collide with a wooden shelf until the power began to dissolve, which Evolto suspected that Vernage's soul is disappearing before firing a crimson energy wave at Misora, knocking her out. Evotlo then asked Ryuga if he'll accept the deal and demanded an answer now as Ryuga cradles the unconscious Misora.

Accepting the deal, Ryuga lead Evolto to the location of the Pandora Box: a museum. Evolto commended Ryuga for going far to save Sento, even when he tried to kill him. Ryuga asked what he meant and Evolto revealed the true reason why he erased Sento's memory as Katsuragi: it was because Katsuragi discovered both Ryuga and Evolto's true identity, which confused Ryuga more. Evolto reminded him of their power being the same, and revealed the reason why: they are both one in the same, meaning Ryuga is a part of Evolto and when they combine, they will give birth to the true Evolto. Horrified, Ryuga tried to deny it, but Evolto told him it's the truth and that Katsuragi called them both to his apartment so he can kill them. As Ryuga pondered over this revelation, Kazumi and Sawa arrived with a dying Sento and all of the Touto Fullbottles in an ambulance. Ryuga walked toward Kazumi, who exited the van with a briefcase containing the bottles, handing it to Ryuga as he presented it to Evolto, telling the alien to cure Sento before giving him the case. Laughing, Evolto told them to kill him in order to purge the poison from Sento's body, which Ryuga and Kazumi chose to oblige as they transformed into KAmen Riders Cross-Z Magma and Grease. Placing the Evol-Driver on, Evolto told them they're no match for him as he transformed into Kamen Rider Evol.

Cross-Z Magma and Grease lunged forward, performing combo attacks and blocking Evol's assaults, gaining the upper hand with a combined Volcanic Attack and Scrap Finish Rider kicks, which forced Evol back briefly. Rising, Evol commended their teamwork before deciding to take them down one by one as he fires his Transteam Gun to push Cross-Z aside, allowing him to attack Grease with combined assaults from his Steam Blade and gun. As Cross-Z attempted to assist Grease, Evol kept pushing him aside as he overwhelms Grease before finishing him off with a Cobra Steam Shot from his Steam Rifle, knocking Grease out of his transformation. Angered, Cross-Z continues the fight, which Evol noticed his Hazard Level has risen to 4.7, but told him he can do better than that and called him partner, but Cross-Z denied it and said Sento is his partner. As Cross-Z continues his barrages, Evol asked him why he's wasting his time protecting the humans as it was their vile greed that led to this war as Sento's condition worsen. Cross-Z shrugged Evol's claim and continues the fight, stating all the people he knew has fought hard to protect someone, willing to sacrifice themselves to protect their happiness. Taking Cross-Z's punches, Evol measured his Hazard Level, which has risen to 4.8, and mocked him for acting like a human before telling Cross-Z he's a part of him, a killer who has slaughtered countless lives. As Cross-Z continues denying it, Evol told him to wake up as he performed an Evoltic Finish Rider kick, knocking Cross-Z out of his transformation.

Evol claimed his victory, but Ryuga stated he hasn't won yet as he pulls out the Dragon Magma bottle. However, Kazumi warned Ryuga that it's dangerous to transform once again after being forced out of the transformation. Evol became amused and wondered what Ryuga will do, who decided to transform again as he accepted risking his life to save Sento. Cross-Z Magma shrugged off the effect and continued the fight, which lead into the blackness of night, his body surging in magma as Kazumi told him to stop, which Cross-Z ignored before engaging Evol again. Evol commended Cross-Z as a part of him began to emerge in Cross-Z's personalty before swinging his flaming Steam Blade at the Kamen Rider. Both riders trade blows before Cross-Z delivers a powerful punch, which raised his level to 4.9. Happy, Evol told him to keep going while Sento nears the end of the poison's course with his heart rate skyrocketing. Summoning all the power he can, Cross-Z delivers a power magma punch, which rose his level to 5.0 as the punch forces a satisfied Evol back. As Cross-Z prepares for a Volcanic Knuckle Rider punch, Evol took the chance to activate an Evoltic Finish Rider punch as both riders ran toward one another, connecting their punches which caused a feedback before exploding.

During the feedback, Evol abandoned Soichi's body and entered Cross-Z, merging with his split genes and becoming whole once more. With the smoke clear, Evolto, now in Ryuga's body with hair unbraided, turned and removed the poison from an unconscious Sento's body, who came to. Shocked, Kazumi asked how Ryuga did that, which Evol spoke with his, saying he's nice to help an enemy in need. Evol placed the Evol-Driver on, unveiling a new Dragon Evolbottle as he inserted it in the belt with the Rider bottle, and transformed into a new form he called Phase 2: Kamen Rider Evol Dragon. As Sawa helped Sento out of the ambulance, Evol confirmed he has taken over Ryuga's body before using telekinesis to grab the Touto bottles and proceeded inside the build for the Pandora Box. Melting the door to the room, Evol walked through and spotted the box, rejoicing as the final stage of his plan comes to fruition until a weakened Sento stood behind him, telling the alien rider he won't let him take the box. Evol asked him if he can fight in his current condition, which Sento told him to shut it and vowed to protect the artifact as he transformed into Kamen Rider Build RabbitRabbit.

Setting the briefcase down, Evol obliged Build and caught Build's punch as the rider asked him why he possessed Ryuga, which Evol revealed to Build that he and Ryuga were once the full Evolto that destroyed Mars and explained how his essence traveled to Earth by hiding in an unmanned probe 23 years ago, and that essence enter Ryuga's mother, but instead of taking over her body it merged with Ryuga as a fetus, at the same time delivering powerful blows to Build. He then stated that when Ryuga was born, the essence lost both of Evolto's powers and memories, which Build asked Ryuga was really part of Evol. Shocked, Evol asked him if he had suspicions, which Build denied angrily as he punched him before Evol seized him by the neck, stating he came to Earth by possessing Soichi ten years ago in order to claim the part of himself in Ryuga before activating an Evoltic Finish Rider punch, cancelling Build's transformation as he fell to the floor. Evol then revealed to Sento that he went to visit his father Shinobu as he failed to open the Pandora Box in Soichi's body and learned he was studying Ryuga, and lied about threatening Sento's father in order to make him work for Evol, while in reality Shinobu chose to ally himself with Evol. Evol then stated it was Shinobu who restored the Evol-Driver as he sat down in front of Sento, who asked him if that's why his father killed himself, which Evol lied and agreed, and continued to explain that he raised Ryuga's Hazard Level, since the beginning, to 5.0 in order for Evol and Ryuga to merge.

Ending the conversation, Evol got up and walked to the Pandora Box, but Sento grabbed his leg, forcing Evol to kick the defeated rider as he revealed the true reason for curing Sento of the poison: he has one more task for him as he grabbed both the box and case, bidding farewell to Sento before leaving at hyperspeed. The next day at the Pandora Tower, Evol presented the Pandora Box to Namba and Utsumi, but Namba claimed Evol deceived him so he can reclaim the Evol-Driver. To keep his fake loyalty intact, Evol stated that it's true he is the only one who can use it, meaning he is the ultimate weapon Namba wanted and preached to still being loyal. Pointing out the Pandora Box, Evol watched as Namba accepted his lie and cradled the box, stating there's one more Fullbottle left to retrieve before he can wield the forbidden energy to rule the world.

After watching Sento and Kazumi attempt to ask Gentoku to help them and keep the Phoenix bottle from Faust, Evolto teleported into nascita, which Misora thought it was Ryuga until Kazumi told her it's Evolto. Praising Kazumi's words, Evolto extended an offer to a ceremony he's having, but excluded Vernage as he knocked Misora out with his power before teleporting the three remaining riders to the center of the tower. Standing next to the Pandora Box, Evolto pulled out the red Pandora panel with the Hachi, Sensuikan, Same, Bike, Rhino, Dryer, Shika, Pyramid, Bat and Engine Fullbottles, asking the humans what they thought of his power as he set the panel on the box, activating the third level of the tower. Placing the Evol-Driver on, Evolto told them he'll be taking the Phoenix bottle before inserting the Cobra and Rider Evolbottles in the belt, transforming into Kamen Rider Evol Cobra as Sento, Kazumi and Gentoku transformed into Kamen Riders Build RabbitRabbit, Grease and Rogue. Even outnumbered, Evol held his own with no effort as Build, Grease and Rogue executed combo attacks, even deflecting Grease's Scrap Finish Rider kick with an energy burst. Rogue then engaged Evol after giving Build the Phoenix bottle as Evol pulled out the second green Pandora Panel, dodging a couple shots from Rogue's Nebulasteam Gun and taking it from him, but Rogue executed a Crack-Up Finish Rider kick that connected, forcing Evol to drop the panel. Spotting Build running to the panel, Evol fired the gun at him until Grease grabbed him from behind to allow Build the chance to get to the panel, but Evol shot Grease in the face before firing a combustive energy at the Hokuto rider, sending him flying out of the tower.

As Evol proceeded to the panel, Rogue intercepted it and tossed it to Build before knocking the gun from Evol's hand before Evol seized him and told him his crimes won't disappear by playing the hero now before sending Rouge flying out of the tower with an Evoltic Finish Rider punch. Seizing the chance, Build took the Kaizoku and Densya bottles and transformed into Build KaizokuRessya Hazard and fired the Kaizoku Hassyar at Evol, who countered with fire energy burst from his fists, stating Build can now endure the Hazard Trigger longer as he reached the panel and pulled out the Gatling bottle. As Evol removed the Cobra bottle and placed the Gatling bottle in its place, he summoned the Hawk Gatlinger while stating he's seen Build's current form before firing a Kikanhou Finish/Full Bullet combination to counter Build's Kaizoku Densya Rider shoot, which both blasts cancelled each other out. Evol saw Build placing the Dragon and Lock bottles in his Build Driver and transformed into Build KeyDragon Hazard before running and deflecting Evol's shots with the Beat Closer. Dodging Build's sword, Evol commended him for fighting with a memento from Ryuga, which Evol deciding to do the same as he tossed the Hawk Gatlinger aside and pulled out the Dragon Evolbottle, inserting in place of the Gatling bottle, and transformed into Evol Dragon. Shocking Build, Evol summoned his own Bleat Closer and asked Build if he can beat Evol's current combined strength with Ryuga as their blades clash. During the fight, Build sensed the Trigger's effect starting to kick in, which allowed Evol to strike him hard, but also allowed Build the time to transform into Build TankTank before he went berserk.

Evol blocked Build's shots from his Fullbottle Buster while moving forward, placing his weapon in a lock with Build's as he told him even if he uses the Rider System to protect the innocent, it's still a tool of war, but Build stated it started with the alien before converting the Buster into blade mode. Build told Evol as he striked him hard with his weapon that if it wasn't for him, Japan wouldn't have been divided into three, leading to war, but Evol told him even if he didn't come, the human race would've eventually gone to war with one another. Build paused, allowing Evol the chance to strike him more with his sword as he reminded him science leads to destruction as the more technology advances, the humans will stop thinking, eventually leading to war. Grabbing Evol's weapon, Build claimed the human race isn't simple, that even if they make mistakes they study them over so they don't repeat them again. Build then claims that's the true duty of science and he'll continue to believe in humanity as he begins to overpower Evol, forcing him to the ground until Evol mimicked his voice as Ryuga, pleading Build to save him. As Build bought the ruse, Evol took the chance to insert the Dragon Evolbottle in his Beat Closer, executing a Dragon Smash Slash, defeating Build as his transformation comes undone and dropping the Phoenix, Dragon, Lock, Kaizoku and Densya bottles.

Evol joked about the voice as he retrieved the bottles, placing the four bottles back in the panel and setting it in the Pandora Box, activating the fourth level of the tower, while also causing a dark cyclone and purple lightning to appear. Evol turned left to see Utsumi, who was ordered by Namba to stop him as he saw Evol was planning to open the box now, telling him to stop, but paid no attention as he fired an energy wave at Utsumi, knocking him out. Evol then pulled out the second red Pandora panel with the Tora, UFO, Kujira, Jet, Kirin, Senpuki, Penguin, Sukebo, Obake, and Magnet Fullbottles, placing the panel in the tower and triggering the tower's fifth level. Holding the final Pandora panel with the remaining bottles, Evol declared the human race to face despair as he placed it on top of the box over Sento's yell, activating the tower's complete erection, and the ground both he and Sento stood on rose to the top and reconfigured itself into ruins. With the tower complete, Evol declared the end of Earth has begun.

Unveiling Project Build's True Purpose & Unexpected Rabbit Possession
1="Why do you think I caused this war? So I could use you to restore my own power! For a human, there's a limit to how much of the energy in this that can be used. That's why I took advantage of the power of science. If a war began, you'd have no choice but to strengthen the Rider System, whether you liked it or not. And with this power, you would become the ultimate Kamen Rider. That's what Project Build really was about!"

- Evolto explaining the real reason he started the war for the Pandora Box and the true purpose of Project Build to Sento.

2="Too bad his plan came to nothing."

- Evolto, revealing to Ryuga, that he has possessed Sento's body.

3="Phase 3, complete."

- Evolto transformed into his new third form: Evol Rabbit.

With the wind blowing wildly from the tower's completion, Evol thrusted his hand in the Pandora Box and pulled out a rusted relic, which drained the essence from all the sixty Fullbottles. As Sento asked what the relic was, Evol said it's the true power of the box called the Evol-Trigger. Evol pressed the button as Sento attempted to rise against the wind, but nothing happened with the trigger. Evol then noticed the trigger hasn't been restored yet as the wind died, telling Sento the Earth's destruction won't come that easily until they both spotted the depleted Pandora Box shaking and turned to see Vernage awaken in Misora's body. As Vernage raised Misora's hand, Evol went flying back to one of the ruins' columns, pinned against it by the Martian Queen's overwhelming power. Evol watched in his struggle as Vernage teleported herself, Sento and the box away before Evol fell to the ground. Amused, Evol decided to let them go and decreed they won't be able to resist the Earth's destruction for long while gazing at the rusted trigger.

Returning to the Seito capital, Evol told a furious Utsumi to calm down before turning to Namba, reminding the disguised human's goal was to show the world the power of Namba Heavy Industries, and now the populace will buy it with the Pandora Box open. Namba asked him he opened the box for them while eating, which Evol realized he bought the lie and assured them he did before stating they can now conquer Touto. Evol told Namba to address his victory to all of Japan as he says Namba's pledge and takes his leave, but Namba told him to retrieve the box, irritating the alien rider while obeying as he leaves the office.

Irritated, Evolto headed to Touto and watched two Hard Guardians, a Flying and Strong Clone Smash attack the humans. He snapped Ryuga's fingers as Namba, with Mido's face, declared victory over Touto through a live broadcast. He then turned to see Sento and Kazumi running to him before stopping to transform into Kamen Riders Build RabbitRabbit and Grease. Evolto stood as the Hard Guardians and Clone Smash engaged the riders, which led to Grease separating the Clone Smash from the fight as Build Fire his Fullbottle Buster as the Hard Guardians, destroying one and sending the second flying to Evolto, who punched it into the ground and destroyed it before transforming into Kamen Rider Evol Cobra. Evol moved at hyperspeed to dodge Build's shots and engaged him until Build placed the Buster's barrel at Evol's torso and fired, sending him flying into Build, who used his own hyper speed and stretched his arms across the ground, and sling-shot Evol to a pillar.

Shrugging off the collision, Evol rose to his knees as he saw Build transform into Build TankTank, with the Tank Armor firing at the alien rider before being placed on Build. To Evol's surprise, Build fired a Fullbottle Break with the Spider Fullbottle, trapping him in a web and shooting hot air with the Dryer bottle inserted in the Buster. Sensing Build can now match his Phase 1 form, Evol transformed into his Phase 2 form and moved at hyperspeed to Build, attacking him aggressively while driving him back. Summoning his Beat Closer, Evol had Build on the ropes and paused by Namba's claim to show the world Japan's true power, which he found amusing and that proved his claim about humanity's greed or foolishness having no limit as he slashed Build with a Smash Hit. Build claimed it's not true before he told Evol they'll put an end to this war, pulling out a folded green Pandora panel and placed it in the Build Driver. As he spun it, his body reacted violently to it with blue lightning erupting from it until Build forced his body to accept it as Evol blocked a stray bolt with his sword, realizing Build has raised his own Hazard Level.

Seeing Build walking towards him, Evol swung his weapon at Build, but it didn't affect him as Build swung a punch at Evol, sending him flying into a pond with a loud splash. Getting out of the water, Evol stated Build's level is at 6 as he commended Build for surpassing human limits and stated he's the same as the rest of the foolish humans. Build asked what he meant by that, and Evol the real reason he started this civil war and Project Build's true purpose: to use Build to restore Evol's own power. Pulling out the Evol-Trigger, Evol revealed that a human can use the device to a limit based on the amount of energy one possesses, and by using science, Build would be forced to strengthen the Rider System as the war escalated as it did now. As Evol praised him for becoming the ultimate Kamen Rider, Build became enraged and attempted to punch Evol, but the alien rider dodged it with hyperspeed and placed his hand in Build's torso, which was part of his plan to become complete and restore the trigger by taking Build's body. After forcing Ryuga out, but keeping his genes with him, Evol became confused as Build turned the Vortex Lever, and was told by him to read his Hazard Level now. Obliging him, Evol was shocked to notice that Build's level was rising rapidly from 6 to 6.1, 6.2, and 6.3 until it kept going, horrifying Evol as Build also revealed he learned of his plan from his father's data and chose to fall for Evol's trap to save Ryuga. Evol then asked Build if he knew what would happen to someone if one's Hazard Level rises quickly, which Build stated he'll die with Evol as he grabbed the alien rider's arm. As Build declared this to be their end, Evol became enraged as he refused to accept being bested by a mere human as he tried to break free, but Build held on tightly until his body reacted to the increased power, causing an explosion.

Instead of killing them however, Evolto was able to possess Sento's body as his transformation was cancelled, forcing them to pass out and turned Sento's hair white. As Ryuga came to, he saw Sento's body lying next to him and tried to wake, which made Evolto regain consciousness. Marveling at Sento's white hair, Evolto stated his plan was sound, even if it didn't work before rising up. Ryuga seized him as he realized Evolto has possessed Sento until Evolto forced Ryuga back with an energy wave. Grease, who witnessed the entire event, ran to Ryuga's side as Evolto placed his hand into his torso, which phased through, and pulled out a red Evolbottle with a rabbit symbol. Accepting this new power, Evolto placed the Evol-Driver on and inserted the new bottle with the Rider bottle and transformed into a new form: Evol Rabbit, which he called it his Phase 3 form.

The Ultimate Phase: Black Hole
1="Revive, my true power!!"

- Evolto activating the revived Evol Trigger after it absored the energy from Cross-Z Magma, Grease and Rogue's Rider Kick energy.

2="Phase 4 complete. Thanks to you, I'm complete again."

- Evolto thanking Banjo and the reawakened Katsuragi.

As Grease and Ryuga stood conflicted at his new form, Evol pulled out the Evol-Trigger and attempted to activate it, but wasn't shocked to see it didn't work as he suspected, even with Sento's drastically increased Hazard Level. Evol shouted in frustration as Ryuga demanded him to return Sento now while placing the Dragon Magma bottle in the Cross-Z Magma Knuckle, then set it in his Build Driver to transform, but to his and Grease's surprise, nothing happened. As Ryuga spun the lever and wondered why he can't transform, Evol revealed to Ryuga that he absorbed all the genes in Ryuga's body, stripping him of his Hazard Level and rendering him a mere human. As Grease realized he's the only one left standing, he engaged Evol to save Sento but found his attacks unaffected until Evol kicked him to the ground. As Grease rose back up and grabbed him, Evol stated he's seriously angered that the Evol-Trigger hasn't been restored before tossing the Hokuto rider in the air and performing an Evoltic Rider kick, sending Grease to the other side of the pond before cancelling his transformation and rupturing the Robot Sclashjelly.

As he was planning to leave, Evol decided to take the Pandora Box and proceeded until Ryuga attempted to stop him and failed, biding him farewell and teleported to nascita. To his shock, Evol saw the entire cafe and the basement gone, leaving a crater in the building. Evol, exclaiming in anger, realized Vernage used her power to teleport the entire cafe and the basement to a new location. Returning to the Pandora Tower, Evol stood silent as Namba told him he learned his alien origin and that he destroyed Mars. As Namba demanded to talk to him about this information, Evol told him he wants to restore his power in order to control the Pandora Box and he should've become complete after absorbing Sento's Hazard Level. Holding the rusted trigger, Evol revealed his next plan: seek power beyond Hazard Level 6 to restore the Evol-Trigger, which is a futile task. Namba then asked what he'll do, and Evol told him he'll wait and see what happens, and stated he'll still be cooperating with Namba, who told him adamantly to retrieve the Pandora Box. Evol, becoming more irritated, chose to oblige Namba's command.

Cancelling his transformation, Evolto called Ryuga with Sento's Build Phone, asking him where they're hiding. As Ryuga asked what he wants, Evolto told him the Pandora Box and demanded it brought to him in one hour, but Ryuga declined. Rising from the cube he was resting on, Evolto asked Ryuga if he was okay with losing Sento, as he threatened to erase his identity once again and told him he has the upper hand before hanging up and tossing the phone over his shoulder. Sensing that Sento's consciousness is aware since his possession, Evolto told him it's his fault and for his defiance, the alien will destroy everything he held dear by starting with his friends.

Waiting for Ryuga and Kazumi in a two-level open building, Evolto stretched Sento's body as he sensed Engine and Remocon Bro's approaching from behind, realizing Namba no longer trusts him. Turning to them, he stated he's fine with them watching him until Ryuga and Kazumi came with the box wrapped in a cloth. Evolto told them to show him the box, which they did and Ryuga demande Evolto to release Sento, which he declined and told them he plans to kill them in front of Sento's eyes. Kazumi then told the alien they'll take Sento back by force and transformed into Kamen Rider Grease with a new Robot Sclashjelly. Evolto wondered what those two can do as he turned and told the Washio brothers to fight them. Leaning over a railing, Evolto watched as Grease fought the Washio brothers, and noticed Ryuga attempting to fight with the Dragon Magma bottle in his hand, as he used to fight before becoming a Kamen Rider, but failed as Engine Bro's pushed him aside and joined Remocon Bro's against Grease. Yawning, Evolto became bored as Grease overpowered the Bro's wielders with a Castle Discharge Crush kick and attempted to finish them off with a Kuwagata/Fukurou Twin Finish thrust until Evolto stopped him with an energy burst, allowing the Washio brothers to gang up on Grease until Kamen Rider Rogue entered the battle, deflecting the brothers' energy gears back at them.

Evolto watched as Rogue overpowered the brothers and defeated Engine Bro's with a Crack Up Rider Punch and the transformed Hell Bro's with a Crack Up Rider kick. Amazed, Evolto walked behind Rogue and placed the Evol-Driver on, transforming into Kamen Rider Evol Cobra. Rogue told Evol as they fought he won't let Japan fall under his control, which Evol asked him if he plans to take his deceased father's place, but Rogue admitted he can't fill the same role as leader of Japan but he can help lay the stepping stones for someone who is and vows to fight for love and peace. Rogue then told Grease to fight with him, which the Hokuto rider obliged and joined the battle, overpowering Evol until he transformed into his Evol Rabbit form, deciding to get serious as well. As Rogue and Grease engaged again, they found themselves outmatched against Evol as he called them a poor fighting pair while blocking Rogue's attacks with Grease's body. After kicking Grease off the second floor, Evol viciously attacked Rogue until Ryuga grabbed him, only to get tossed aside by the alien rider, unaware he took the Dragon Evolbottle. Turning his attentions back to Rogue, Evol used his power to hold Rogue long enough for him to generate an Evoltic Rider punch, knocking Rogue off the second floor next to Grease.

As Evol proceeded to both riders, Ryuga called him out and revealed he has the Dragon Evolbottle, stating it was created from his body, but Evol stated he can't handle the power it possesses. Ryuga stated he knows, but vows to still do it as he engaged Evol with weak punches, which Evol found nostalgic from their early days of combat to increase Ryuga's Hazard Level. Countering with superior attacks, Evol told Ryuga the only difference this time is that he no longer has his essence as he backhanded him down a row of stairs. The beaten Ryuga, however, refused to concede and rose up, running back to Evol and throw more punches as Evol stated it won't work until the third punch fazed Evol with blue flames. The surprised Evol was punched twice again with the blue flames emanating from Ryuga's fist and wondered how Ryuga was able to do that as the dragon Evolbottle turned gold. What shocked Evol more was that Ryuga placed the transformed Evolbottle in his Cross-Z Dragon, which changed its color to crimson, and placed the altered device in his Build Driver, re-administering his Hazard Level 5 in his body and transformed into an altered Cross-Z: Kamen Rider Great Cross-Z. As Great Cross-Z engaged him, Evol realized small fragments of his essence remained in Ryuga and his will forced them to multiply into new ones, but he told Cross-Z he's still not a match for him as he forced the rider to the first floor and kicked him to the ground. Great Cross-Z pulled out the Cross-Z Magma Knuckle and transformed into Cross-Z Magma and countered Evol's punch with a more power one, which the alien rider realized his strength has improved since his previous incarnation of Cross-Z Magma.

As Evol found himself being pushed back by Cross-Z Magma's punches and Volcanic Finish Rider punches, Rogue and Grease joined Cross-Z and executed their Rider kicks, which Evol realized their wills is the source of their Kamen Rider powers and decided to take that power by using the rusted Evol-Trigger to block their kicks. in front of his eyes, Evol saw the rusted device restored to its black and white color scheme, using it to create a feedback that knocked the riders out of the sky. Sensing his completion is near, Evol activated the Evol-Trigger as he decreed his true power revived, creating a black cyclone that sent the three riders flying in the air. Placing the trigger in the Evol-Driver, Evol jumped from Sento's body, which went flying out of the cyclone, solidifying Evol's essence to restore his original body. Completing his transformation, Evol dispersed the cyclone to reveal his complete form to the depleted riders: Evol Black Hole. Landing back on the first floor, Evol noticed Sento has regained his memories as Takumi Katsuragi and lost his memories as Sento Kiryu. Evol thanked both Katsuragi and Ryuga for their roles in helping him regain his true form until Kazumi and Gentoku caught up to Evol, who asked them if they still plan to fight even after being forced out of their transformations. Not surprised, Gentoku, Kazumi and Ryuga shrugged off the aftereffects and transformed into Kamen Riders Rogue, Grease and Great Cross-Z before engaging Evol, who demonstrated his true power and strength to the human riders. Evol scolded them for fighting him with their current injuries as he easily overpowers them, even when Grease, Rogue and Great Cross-Z executed their Rider kicks, which he stopped with his black hole energy, vowing no one can fare against him in his true form before blowing them away. Realizing they're at a severe disadvantage, Rogue stated they need to withdraw and regroup as he pulled out his Nebulasteam Gun and typhoportated himself, Grease, Cross-Z and Katsuragi away.

Evol stated that was wise for the human riders to retreat as he moved with hyperspeed to the Pandora Box, removing the Evol-Trigger from his driver and placing it in the box's opening, which used its energy to enfold the bottles within once more while creating a black panel to fill up the void by the remodeled green panel. Grabbing the black panel, Evol placed the Cobra and Bat Fullbottles on the first row, which turned the bottles black and gold. As he inserted the Shimauma and Hasami bottles in the second row, Evol vowed to use this new power to evolve himself even further as the second bottle set turned black and gold, declaring the final chapter has begun.

Returning to Namba Heavy Industries as a replica of Soichi Isurugi, Evolto presented the Pandora Box, minus the black panel, and all the Fullbottles to Namba, Utsumi and the Washio brothers as a woman played Namba's piano. Namba asked if Evolto possessed Isurugi again, but the alien revealed that his completed form has the ability of shape-shifting and no longer needs a host. Placing the box and bottles down, Evolto decided to drop the loyalty facade and declared himself the ruler of Japan, which shocked everyone in the room. As Utsumi asked what he meant, Evolto stated that Namba can still act in Mido's place, but he must answer to Evolto now, who demonstrated his shapeshifting power by turning into Namba. Namba, angered, asked if Evolto's insulting him and refused to comply as Evolto turned back to Isurugi, stating he can kill the elderly human right now but told him to think it over and reveal his answer by tomorrow instead. As he leaves, Evolto told Namba he's confident he'll make the smart choice, angering the human as he slammed his cane on the ground.

Later on, Evolto teleported to the science lab in Namba Heavy Industries as Utsumi injected the Washio brothers with more Nebula Gas to raise their Hazard Levels. The alien walked to Utsumi, and presented a replica of the Evol-Driver, shocking Utsumi who asked why he has a duplicate, but Evolto told Utsumi it's for him and as an offering to join him. Evolto then told him to see it as payment for his scientific knowledge before teleporting, leaving Utsumi conflicted. The next day in the Pandora Tower, Evolto waited for Namba's response as Utsumi walked in and activated the webcam function on his iPad that's connected to Namba's computer in his building. In the webcam, Namba gave his answer in the form of the Washio brothers and a group of Heavy Guardians approaching behind Utsumi. Realizing this declination, Evolto commented on Namba's decision to keep his power as the Washio brothers transformed into Engine Bro's and Remocon Bro's, which Evolto decided to accept the fight and activated the Evol-Trigger and placed it in the Evol-Driver, stating today Namba will die as he placed the Cobra and Rider Evolbottles in his driver, transforming into Kamen Rider Evol Black Hole. Placing his hand on the floor, Evol triggerd the tower's power and telported himself, Utsumi, Engine Bro's, Remocon Bro's, and the Hard Guardians to a small canyon with broken clocks, mirrors and cubes. Utsumi made the first move and signaled the Hard Guardians to attack, but Evol destroyed them all with a wave of his hand, shocking Utsumi as Engine Bro's and Remocon Bro's advance to attack Evol.

Evol stood still as he body remains still from Remocon Bro's Nebulasteam Gun shots until he dodged Engine Bro's' swipes with his Steam Blade, countering their moves with his own while criticizing them. Even as the Bro's wielders' attacks didn't faze him, Evol knocked them to the sand and kicked Remocon Bro's aside while uppercutting Engine Bro's in the air, who stated their increased Hazard Level should've made them stronger. As Evol approached Engine Bro's, Kamen Rider Great Cross-Z attacked from behind, who entered through a portal from the Pandora Tower with Kamen Riders Rogue and Build RabbitRabbit, who displayed trouble with utilizing the RabbitRabbit form as Katsuragi has no knowledge on using Sento's upgrades to the Rider System. Even with the three riders assisting Remocon Bro's, Evol stilled proved to be superior as he scolded them for thinking they can win with more numbers. Having enough, Evol blasted Rogue and Cross-Z and knocked Remocon Bro's aside while engaging Katsuragi solo, who stated he can't keep up with the RabbitRabbit form and Evol agreed while adding that Katsuragi can't use the new additions to the Rider System well enough as he tossed him in the sand. Rising, Katsuragi told him he designed the Rider System to kill Evolto and engaged him, but Evol knocked him aside, forcing Katsuragi to place the folded Pandora panel in place of the FullFull RabbitTank bottle and turned the Vortex Lever, but the power was too much for his body, allowing Evol to attack with his black hole energy, knocking Katsuragi to the ground and cancelling his transformation.

Deciding playtime is over, Evol decided to keep his promise and generated a miniature black hole, shooting it at Engine Bro's. As the black hole consumed Rai, he tossed his Gear Engine to Remocon Bro's before his body dissolved into white energy that was consumed completely by the black hole. Seeing his brother's death, Remocon placed the Gear Engine in his Nebulasteam Gun and transformed into Hell Bro's, running at Evol in a rage. Even with the Gears combined, Evol overpowered Hell Bro's, knocking him to the ground as Cross-Z transformed into Cross-Z Magma, and engaged Evol. While Hell Bro's gazed at Cross-Z's conviction to keep fighting, Evol overpowered him while stating changing forms won't affect the outcome and unleashed an energy punch, cancelling Cross-Z's transformation as he's flung into the sand. Turning the Evol-Driver's lever, Evol told Ryuga it's time to die as he unleashed a Black Hole Rider kick, but Hell Bro's pushed Ryuga aside and took the attack on, killing him. Falling to the ground, Ryuga seized the dying Fu, asking him why he did that, which Fu stated it's not a bad feeling to save someone as his body disintegrates in a green light. Turning to Katsuragi as he asked why human lives are lost, Evol told him it's because of the Rider System before opening a portal to Namba's office and went through it.

As Namba fell to the floor, Evol watched him cower in fear and begged to be spared and offered to give him money while he told Namba he gave him a chance. Seeing Namba beg made Evol laugh, who grabbed and hugged Namba as he told him he loves the human race for being pathetic creatures, making Namba think he's been spared until he injected poison to the elderly human, ending his life. Returning back to the battlefield, Evol turned to Utsumi, who watched Namba's death from his iPad, and tossed Namba's cane on the sand, offering him a choice: avenge Namba or accept his offer from the previous day. Evol watched Utsumi take Namba's cane and suffer a mental breakdown, laughing as he broke Namba's cane and declared loyalty to Evol, which shocked Rogue. Breaking down laughing, Evol found the human race amusing and decided not to destroy Earth before tossing the second Evol-Driver to Utsumi, who placed it on and inserted the Bat and Engine Fullbottles in the driver, turned the lever to administer Hazard Level 5 Nebula gas into his body, and transformed into a Kamen Rider, which resembled Night Rogue's suit. Marveling at the new rider, Evol christened Utsumi's rider form Kamen Rider MadRogue and told him to fight to his heart's content.

Evol witnessed MadRogue turn to Rogue and proceeded to attack him, stating the former Faust member he doesn't care about betraying Japan as long as his scientific abilities are utilized while overwhelming Rogue with a combination of some shots from his Nebulasteam Gun and slashes from his Steam Blade. MadRogue then overwhelmed Rogue with an Evoltic Attack Rider Thrust, cancelling his transformation and prepared to finish him and Ryuga off with a Funky Shot from his Nebulasteam Rifle until Kamen Rider Grease, who refused to assist Namba Heavy Industries, arrived and deflected MadRogue's shot with a Castle Discharge Crush shield, then proceeded to typhoport himself, Ryuga, Katsuragi and an unconscious Gentoku away, leaving Evol and MadRogue in the small canyon. Evol said aloud it's no use for them to run as they no longer have a future.

That evening at the Pandora Tower, Evol unveiled his new plan to Utsumi as he held the black Pandora panel with the four bottles: he plans to act as Seito's prime minister now that Namba's dead, they'll destroy Touto and reunite Japan as one nation, all to obtain their true goal. Utsumi asked what they intend to do with the Kamen Riders, which Evol stated he still has a use for them and told Utsumi to bring them in alive, the true reason he gave the human a copy of the Evol-Driver. Utusmi stated how Evol had another one considering his is the only one to exist, but Evol told him it's none of his business and just do what he's told to, keeping the fact the second Evol-Driver was built by Shinobu Katsuragi, who was believed to be dead, hidden. The next day, Evol watched as Utsumi lead a squad of Hard Guardians mount an attack on the Touto capital to draw out the Kamen Riders, which Great Cross-Z and Grease came to stop them, later on Katsuragi came to fight Kamen Rider MadRogue. During the fight, Evol witnessed Katsuragi reverted back to Sento Kiryu and transformed to a new form: Kamen Rider Build Genius.

Quest of the Lost Bottles
Evol watched as Build Genius overpowered MadRogue with his new powers and defeated him with a combination of a Genius Attack Rider punch, followed by a Genius Break Rider kick. Seeing enough, Evol teleported to the capital and commended Build for concealing such a weapon that could rival Evol's power. As Build prepared to fight, Evol assured him they will in time as he moved at hyperspeed to Kazumi, punching him in the gut, forcing him to drop the Castle, Kuwagata and Fukurou Fullbottles. As he picked them up, Evol told Build, Ryuga and a furious Kazumi that he plans to use these bottles, which he called Lost Fullbottles, to subjugate the human race and control their future before teleporting away with MadRogue.

That night at the Hokuto Faust facility, Evolto watched as two Faust scientists injected a woman with Nebula gas until Utsumi asked what the scientists are doing. Evolto told Utsumi he's creating the final form of the Smash he called the Lost Smash, which the subject uses a Lost Bottle to fuse with two Clone Smash to become a Lost Smash, a slave to Evolto. Utsumi asked why he's doing this now, which Evolto told him it will be interesting to see greedy humans instill fear into other humans, leading to their own demise and destroy Earth. Utsumi then realized Evolto had never intended to spare the Earth, but instead chose to use the Kamen Riders as Lost Smash to do his work for him, which Evolto who confirmed it and toasted a celebration to the first Lost Smash as the scientists opened the vat to reveal the woman to be Yoshiko Tajimi. The next day, Evolto watched as Tajimi intercepted a captured Kazumi, who sneaked into the facility to take back the Three Crows' Lost Bottles but ended up being injected with a lethal dose of Nebula gas, and transformed into the Owl Lost Smash. As Kamen Riders Build and MadRogue entered the fight, Evolto moved with the fight to the woods and witnessed Kamen Rider Grease overpower MadRogue as his Hazard Level has increased, and Build Genius neutralized the lethal Nebula gas in Owl Lost Smash's body before defeating her with a Genius Finish Rider Kick, which not only reverted Tajimi back to her human form but rid her of the Pandora Box's light within her as well. After Build and Grease defeated MadRogue, Kazumi told Tajimi to atone for her actions in the war and noticed the Fukurou bottle turned black, which Evolto, as Kamen Rider Evol Corba, appeared, expressing his amazement to Sento for returning Tajimi to normal with the Genius bottle. As Kazumi took Tajimi to safety, Evol demanded the bottle and told Sento he'll create a new world with it when asked.

As Evol also said he could help, Sento refused to hand the bottle and transformed into Kamen Rider Build Genius and moved at hyperspeed, engaging Evol and displaying the Genius bottle's power as both riders countered their attacks while moving all over at hyperspeed. Sensing that Build is stronger than his current form, Evol attempted to transform into his Black Hole form until Build grabbed his arm before he could insert the Evol-Trigger and performed a Genius Finish Rider punch at Evol's chest. After being forced out of his transformation, Evolto noticed an odd sensation within him, realizing Build's attack has bestowed on him as a side-effect that he never had before: emotions. Rising to his feet, Evolto praised Build for his ingenuity and the Genius bottle's power, stating he'll take the Fukurou bottle back another time and took his leave. That night, Evolto returned to the Hokuto Faust facility with the Lost Pandora panel, placing it on a display case and examines it, stating he needs the remaining six before sitting down. He listed the emotions happiness, sadness, anger and surprise, saying he used to think of them as imaginary things until Sento gave them to him with the Genius Finish attack. He grabbed Shinobu, who was wearing a mask and worked on a computer, and told him he now knows the meaning of emotions and expressed joy as he never felt this way before.

"I blocked it perfectly...Why?! What is this emotion?! How could I have been beaten by an inferior lifeform like you?!"

- An enraged Evol refused to accept being bested by a human as he ferociously attacks Build.

The next day, Evolto and Shinobu received a call from Kyoichi Shimizu, an assistant of Shinobu and the same person who was the Strong Smash, informing him he has been contacted by Sento and planned to meet him. They told Shimizu to stop by before heading to the meet, but they turned the former assistant into the Stag Lost Smash, telling him he'll if doesn't kill Sento. From the darkness, Evolto, as Kamen Rider Evol Black Hole, watched the Stag Lost Smash fight against Kamen Rider Build Genius underneath a bridge before Build cured him with a Genius Finish Rider kick, reverting Shimizu back to normal, which blackened the Kuwagata Lost Bottle. As Shimizu told Build that his father built the Lost Bottles to be used with a black Pandora panel, Evol generated a tendril and injected Shimizu with poison, killing him instantly. Laughing, Evol told Build it's too bad after wasting all that effort to saving Shimizu, and told Build, who asked why he killed Shimizu, that he wanted to feel the excitement of seeing Build angry as he jumped down from a ledge. Enraged, Build engaged Evol as both riders move faster than the human eye, trading blows until they stopped at the abandoned road and took each other's attacks. Pushing Build aside, Evol executed a Black Hole Rider punch, knocking Build on a sidewalk.

Evol then approached the weakened Build, telling him it's easy to manipulate human emotions and decided to turn Build into a Lost Smash with the very Lost Bottle Shinobu created and injected Build with the Castle Lost Bottle as he praised the idea of the one who proclaims to fight for love and peace will be the one to destroy the world. To his shock, however, Build used the Genius bottle's power to nullify the Castle Lost Bottle, causing the alien rider to pause, allowing Build to kick him. Build told the shocked Evol that his father may have created the Lost Bottles, but that they would be used for justice, he'll never concede to someone who manipulates emotions and vowed to build whatever Evol destroys before executing a Genius Rider kick, that connected through even when Evol was strong enough to block it. Rolling on the ground before rising back up, Evol stated why Build was stronger than his completed form as anger swelled up inside Evol, who then rushed at Build and began assaulting him with such ferocity and stating he won't be bested by a weak human as his own Hazard Level began to rise and his last punch knocked Build to the ground, forcing the rider to drop the Fukurou and Kuwagata bottles. Changing his plans, Evol told Build he'll let him live until the end to see him take all the hope from this world and leave the ultimate taste of despair as he took the two Lost Bottles and teleported back the the facility. Evolto then handed Shinobu the two bottles, who then inserted them in the black panel to turn them black and gold. Shinobu told Evolto he got too emotional, which Evolto stated was just for fun and told Shinobu to accelerate the Lost Smash project as Shinobu took off his mask.

"Death" and Completed Lost Pandora Panel
"Now the door to the new world will open!"

- Evolto proclaiming his victory as he absorbs the Black Pandora Panel with all ten Lost Bottles. At the Hokuto Faust facility, Evolto marveled at the six Lost Bottles and stated a new world will be created once the remaining four are collected. As Shinobu asked him why his killed Shimizu, Evolto told him Shimizu's death was to keep him quiet about his plan with the Lost Bottles and that he's outlived his usefulness after becoming a Lost Smash, but Shinobu pointed out there's no more subjects to create more Lost Smash. Evolto then said they can experiment with the Kamen Riders to purify the remaining four bottles, which Shinobu concurred as their bodies are stronger to handle the Nebulas gas dosage to become Lost Smash while ruling out Sento for his Genius form nullified the Lost Bottles' element. Hearing Shinobu's concern, Evolto reminded him it's his job to find a way around it while expressing his belief in the scientist before turning to Utsumi, who entered the room, telling him he'll reunite Japan today in order to speed up the Lost Smash project.

Executing his plan to reunite Japan, Evolto, as Kamen Rider Evol Black Hole, launched an attack at the Touto capital with a Pressure Clone Smash while Utsumi, as Kamen Rider MadRogue, lead two Hard Guardians to attack a bridge, dividing the Kamen Riders in two as Sento and Gentoku headed to the capital while Ryuga and Kazumi go after MadRogue. Evol was surprised to see Sento and Gentoku before Sento asked him if his father's still alive. Evol pretended to not know what Sento was talking about, but the human didn't buy it and demanded to know where he was until Gentoku reminded Sento of protecting the capital. Chuckling at Sento's suspicion, Evol wathced as the humans transformed into Kamen Riders Build Genius and Rogue and engaged them, counter Build's attacks with his own while Rogue engaged the Clone Smash. Sensing Build's aggravation in his attacks, Evol took it to his advantage as Build asked him where his father was before playing mind games with the rider, asking him if his father's more important than protecting Touto. Enraging Build more to overpower him, Evol summoned his Steam Rifle and inserted his Rabbit Evolbottle as Build forced him back with powerful punches and ran at him, but Evol moved at hyperspeed in a circle around Build, Rogue and the Clone Smash, executing a Rabbit Steam attack at all three, forcing Build to generate a diamond shield to protect himself, but Rogue and the Smash have no protection from the continuous assault, killing the Smash and cancelling Rogue's transformation. Seeing Build become overwhelmed, Evol appeared before the exhausted riders and declared it's showtime as he executed a Black Hole Finish, creating a black hole and tossed it over the capital, destroying it. Evol decreed that all of Japan is now his with the Touto capital gone before taking his leave, laughing as Gentoku and Build gazed at the destroyed building.

Returning to Seito, Evolto shapeshifted into Mido and made a broadcast to all of Japan, stating the civil war is now over and the three segments of the country are now one once more. To see the humans glimmering with hope, Evolto declared to have all weapons not related to self-defense dismantled and promised he'll do his best to repair what the Sky Wall took from the denizens ten years ago before signing off. After the broadcast, Evolto flicked the Seito flag as he morphed back into Isurugi's form, telling Utsumi to capture the Kamen Riders for the Lost Smash project. Ustumi, however, expressed his confusion of how turning the Kamen Riders into Smash that will destroy everything contradicts with Evolto's plan of ruling the country. Evol, irritated, told Utsumi to stop asking questions if he wants to live, which Utsumi realized Evolto will kill him if he doesn't obey him before the alien walks out of the room. From a distance, Evolto and Shinobu, who transformed into Kamen Rider Build RabbitTank with a prototype Build Driver, watched as Kamen Riders Build Genius and Rogue defeated MadRogue, cancelling his transformation before Shinobu revealed himself to Build and Rogue, cancelling his transformation to reveal he was still alive. Clapping as he walked to Shinobu's side, Evolto expressed his amusement at this family reunion before Sento asked his father why he's on Evolto's side as he built the Rider System to defeat the alien. Evolto then revealed that it was all Shinobu's plan to turn Sento and Ryuga into Kamen Riders, leaving Sento crestfallen as Kazumi and Ryuga appeared, the latter refusing to believe Shinobu would deceive his own son. Shinobu showed no concern as he stated all that has transpired from the beginning following the Sky Wall disaster has been by his design and his goal will be complete once all ten Lost Bottles are collected. Evolto then warned the four riders to stop interfering in their plan or they'll suffer the consequences before moving at hyperspeed to carry the injured Utsumi through a portal back to the Faust facility, leaving Shinobu, who transformed into Kamen Rider Build NinjyaComic, to fight Gentoku, Kazumi and Ryuga as Kamen Riders Rogue, Grease and Cross-Z Magma.

After Shinobu returned from being almost killed by an out of control Cross-Z, Evolto contacted Misora and told her to meet him at a railway station. Seeing her approaching from an ascending escalator, Evolto joked about them not seeing each in a while before Misora asked him if she can really save Sento, who has lost hope in what the Rider System was built for, which Evolto replied she can if she obeys him before he knocked her out with an energy burst. That night at the Hokuto Faust facility, Evolto gazed at Misora in the Nebula gas vat as Shinobu administered the element in her. Evolto asked Shinobu if she'll survive the process, which the scientist stated she should, if Vernage's fading powers accept the Nebula gas, causing a catalyst that will restore them to full force. Evolto then stated Vernage's spirit is dying, which Shinobu replied Misora will die as well, amusing Evolto as he pointed out Shinobu's lack of concern before he told Evolto it's all for the new world. The next day, Evolto watched as Misora, under the control of a corrupted Vernage, transformed into the CD Lost Smash and attack Kaman Rider Build with Shinobu, overwhelming the melancholy rider until Ryuga, who'd awaken from losing consciousness as Evolto's genes made him run wild, appeared and assisted Sento, confirming a new resolve and turned the tide of the battle, which lead to the outcome of saving Misora, transferring Vernage's power into Ryuga's body to nullify Evolto's genes, and Sento reacquiring the Rabbit bottle, which turned gold as proof of Sento's Hazard Level rising to seven. That night as a defeated Shinobu returned to the Hokuto facility, Evolto asked him if this was the first time he miscalculated or he did it on purpose, which the scientist admitted he didn't know it would end like that until Utsumi arrived, telling them Kazumi and Gentoku have infiltrated the facility as he showed it on the monitor. Evolto expressed his excitement as he stated the fun isn't over yet.

Watching Utsumi and a squad of Hard Guardians capture Kazumi and Gentoku from the monitor, Evolto noted that with both riders becoming Lost Smash and their Lost Bottles purified, meaning the new world will come sooner now with one more bottle left before heading to the Pandora Tower with the Lost panel. In the tower, Shinobu arrived to inform Evolto of Sento and Ryuga breaking into the facility and rescuing Kazumi and Gentoku, who've already been injected with a lethal dose of Nebula gas to increase their strength, Evolto expressed his annoyance at Shinobu's failure to capture Sento again. Shinobu told him it's because Build's strength has increased again and proposed a new option to Evolto: using his own body to purify the last three Lost Bottles, which left Evolto puzzled and suspecting Shinobu's planning to betray him. After Shinobu told him it's possible now that he has emotions, Evolto, deciding to play his role, contacted Sento that evening and demanded the CD Lost Bottle. Sento told him he won't, but Evolto assured him he will as he's aware of how strong Evolto is, and told Sento he can kill everyone and destroy everything he cared about with his full strength. Before hanging up, Evolto told Sento if he doesn't want to see anyone get hurt, hell hand over the Lost Bottle. The following rainy morning, Sento met with Evolto, as Kamen Rider Evol Black Hole, in an abandoned warehouse, showing the alien rider the black bottle before telling him he doesn't intend to hand it over. Expecting this, Evol rose up and told Sento to prepare himself for the fight until Ryuga, Kazumi and Gentoku arrived, confusing Sento as Ryuga revealed he placed a tracker in the newly built Blizzard Knuckle.

Seeing the four humans stand together, Evol laughed and asked them if they're in a hurry to die, which Kazumi told him they're here to fight for the future of the Earth as Gentoku unzipped his jacket to reveal a kanji saying "I'm with stupid". After all four humans laughed, they transformed into Kamen Riders Build Genius, Cross-Z Magma, Grease, and Rogue as Evol fired a black hole energy at them, which was deflected by their completed transformations. With fire seering behind them from the explosion, Evol told them to come at him with all they got, which the riders did with Grease making the first move with his dual Twin Breakers. Evol dodged them before blocking punches and kicks from Cross-Z, Rogue and Build before getting in a few hits himself until the riders started to double-team against him. Starting to show more of his strength, Evol summoned his Transteam Gun and fired at Cross-Z, knocking him into Build. Evol was caught unguard by Rogue's Steam Blade and one of Grease's Twin Breaker, gaining the upper hand as Evol noticed their Hazard Levels have increased but it's no use against him as he shot Rogue and punched Grease in the head. Build and Cross-Z lunged at Evol, but were quickly knocked back down before Evol moved at hyperspeed and attacked all four riders at once. As both Cross-Z and Rogue realized he's stil not fighting at full power, Evol told them it would be a waste for him to use his power power against a meager species like the humans as he charged crimson energy in his Steam Rifle, firing it at Rogue, then fired a black hole energy from his hand at Grease while he said it doesn't matter who or what the Kamen Riders are fighting for. As Build and Cross-Z charged at him, Evol stated they won't beat him due to the humans being powerless before executing a Black Hole Rider kick, knocking them outside along with Grease and Rogue.

Walking in the dry outdoors, Evol asked the weakened riders if they're done, which Build stated as he rose that human beings are not powerless when they work together, and from that compliance they can turn despair into hope. As Cross-Z, Grease and Rogue rose back up, Build stated they can turn defeat into victory, summoning scientific equations that began spiraling around the four riders. Still not believing Build's words, Evol caught Rogue and Grease's punches as they ran at him, stating it's futile until they grabbed his arms and moved to his sides, allowing Cross-Z to punch Evol with the Blizzard Knuckle. Continuing to attack with the device, Evol told Cross-Z he can't harm him in their current condition before Rogue and Grease executed a Crack Up and Scrap Rider punches, keeping Evol at bay for Cross-Z to execute a Glacial Knuckle Rider punch that hit the Evol-Trigger. The trigger then shorted out, causing Evol to move back before becoming paralyzed, which shocked him even more as the damage reverted him back to his Cobra form. Sensing Build will finish him, Evol spliced off a sample of his essence that then teleported to the Pandora Tower and possessed Utsumi before Build performed a Genius Rider kick, delivering the final blow. Rolling on the grass, Evol rose up slowly as his body began disintegrating, commending the riders for their tenacity to fight even though the fight's not over. Raising his hands, Evol pretened to accept his fate as his body exploded, leaving the Evol-Driver, which absorbed some of his genes, and the now purified three Lost Bottles on the grass.

From the shadows in the Pandora Tower, Evolto watched as Shinobu brought the four riders in with the three purified Lost Bottles and the Evol-Driver in a special container built to suppress the genes stored in the belt. Evolto's suspicions have been confirmed as Shinobu explained to his son, Ryuga, Kazumi and Gentoku that he planned to betray Evolto since the Sky Wall disaster and apologized for his actions before inserting the Castle, Spanner and Hammer Lost Bottles in the black Pandora panel, turning them gold and black, and removing the black panel from the frame before telling the riders to bring the Pandora Box. As Shinobu explained that the completed black panel will allow the wielder to teleport from planet to planet in an instant and the alien had planned to use that power to consume planets more frequently, Evolto, in Utsunmi's body, emerged from the shadows and glowed his eyes red to let all the humans know he's still alive. As a horrified Shinobu asked how he survived, Evolto revealed that after obtaining his complete form, he gained the ability to manipulate his genes at will and spliced off a sample that possessed Utsumi. Evolto then told Shinobu he should've expected for him to catch on to his scheme before generating a tendril and struck it in Shinobu's chest, injecting him with a lethal dose of poison. Placing Ustumi's Evol-Driver on, Evolto transformed into Kamen Rider MadRogue as Ryuga, Kazumi and Gentoku transformed into Kamen Riders Cross-Z Magma, Grease and Rogue before running at Evolto, who did his best to fare against them in Utsumi's body. Overpowering Cross-Z and Rogue, Evolto spotted Grease, who noticed Sento mourning as his dying father disintegrated, and told him not to look away before firing a crimson energy wave infused with his genes at the rider, dealing a critical blow as Rogue caught him and removed his Sclashjelly before his body started to disintegrate. Engaged by Cross-Z again, Evolto noticed he can no fare against them in Utsumi's body as he dodged Cross-Z punch and headed to the container, retrieving his original driver and jumped from Utsumi's body to create a replica body of MadRogue. Inserting the original Evol-Driver on and the Cobra and Rider bottles, Evolto merged with the genes stored in the belt as he transformed in Kamen Rider Evol Corba, and prepred to fight Cross-Z and Rogue, but Rogue called for a retreat as he typhoport an unconscious Kazumi and a distraught Sento with the Nebulasteam Gun while Cross-Z ran for the Pandora Box and the black panel.

Seeing Cross-Z with both the box and panel, Evol summoned the Hawk Gatlinger and fired at Cross-Z, forcing the rider to drop the panel before Rogue shoved Evol long enough to typhoport himself and Cross-Z out of the tower. Tossing the gun aside as he picked up the panel, Evol commented on how close his goal is with just one more Lost Bottle left, waiting for his essence to take control of Kazumi and return with the CD Lost Bottle. As Mido, Evolto announced the relocation of the central government within the Pandora Tower the following day before unleashing an army of Flying Clone Smash to attack the populace. Seeing Kamen Riders Build RabbitRabbit, Cross-Z Magma, and Rogue destroy the clones from a rooftop, Evolto, as Kamen Rider Evol Cobra, laughed at their victory before stating the attack was staged to lure the three riders out and gestured them to come. Watching the three riders stand before him, Evol noticed Build's anger as he vowed to avenge his father and attempted to transform into Build Genius, but was shocked when the Genius Fullbottle didn't activate. Amused, Evol sensed Build has lost his conviction before telling all three riders they've should've noticed he's not in his complete form.

At nascita, Evolto's genes took control of Kazumi's body and rose up, knocking both Sawa and Misora out with a lightning charge. Taking the CD bottle from Misora, the possessed Kazumi moved at hyperspeed to Evol, handing him the last Lost Bottle to Evol before the genes jumped from Kazumi and merged back with Evol. Tossing the unconscious Kazumi to the riders, Evol placed his Evol-Trigger on his driver and transformed into his complete form. Stating he now has all the Lost Bottles, Evol placed the CD bottle in the last slot on the black panel, turning his gold and black before activating the Feverflow function on his trigger and turned the lever while placing the panel in his chest. Evol then stated the door to a new world will open as his body absorbed the panel, triggering a new transformation: a monster form as his body generated a multiple shade of crimson shock waves that woke Kazumi and overwhelmed the three riders briefly. As Build, Cross-Z and Rogue ran at the monster, Evolto knocked them down with no effort before tossing Rogue and Cross-Z to a building close by, generating a fire wave that destroyed the building, which forced the wounded riders to fall back down on the rooftop they're on. Build and a transformed Grease engaged Evolto, who pushed Build aside and knocked Grease down, kicking him in the side with a crimson shock wave that destroyed another building on the opposite side. Brushing off Build's attacks like they were nothing, Evolto seized him by the helmet and activated his new warping power, telling him he'll show the rider a good time before teleporting themselves to the next world after Earth, a heavy vegetation planet with spectral lifeforms. Evolto, seeing Build still in one piece, commended the Rider System for being able to withstand the warping power before stating his true goal since the beginning: consume all the planets throughout the cosmos and recreate the universe in his image. Cranking his lever, Evolto executed a Black Hole break, creating a large black hole in space that destroyed the vegetation planet while teleporting himself and Build out in space to see the green planet's destruction before teleporting back to Earth, which left Build taking much damage while Evolto's power grew from consuming the green planet.

Feeling his power building up, Evolto saw his arms transmutate to the Evolti Grasper gauntlets, and tested them out as he grabbed Build and struck with enough force to send the rider flying threw a tall building before teleporting in the air to intertecpt Build by punching him up and then teleported above the ascending Build to strike him down hard to the ground. Teleporting to the ground in front of an injured Sento, Evolto asked him if he like this new power bestowed upon the alien by his father, then stated he'll be able to destroy every planet more quickly, even Earth. As Sento remembered his promise with his father as Katsurargi, Sento regained his conviction and successfully activated the Genius Fullbottle, transforming into Kamen Rider Build Genius with the Hazard Trigger after brushing off the effects of transforming immediately after being forced out the Kamen Rider form. Seeing himself now surrounded by Build, Grease, Cross-Z, and Rogue, Evolto expelled flames from his body as the four riders jumped and executed their Rider kicks, which blew through the flames and hit Evolto, who felt no damaging effect. Evolto scoffed at their attempt until he noticed the black panel coming out from his chest, now feeling the energy from the Rider kicks affect him until it caused an explosion. Catching the black panel in his hands, Evolto watched as Build executed a Hazard and Genius Rider punch at the black panel, which shocked him even more to see the Castle and Hammer Lost Bottles reverted back to their maroon and purple original forms before the attack ignited an explosion, knocking Evolto back and the two bottles out of the panel. Reverting back to his Black Hole form, Evol wondered how was this possible as he attempted to retrieve the two bottle, but only got the Hammer bottle back as Grease managed to retrieved Masaru's Castle bottle. As Build, Cross-Z and Rogue joined Grease, Evol cursed at the humans and retreated back to the Pandora Tower at hyperspeed.

That evening after announcing the new governors of Touto, Seito and Hokuto, Evol sat in anger over his defeat and the lost of one Lost Bottle. Hearing Utsumi approaching, who realized the alien's plane to rule Japan was just a ruse to complete the black panel, Evol seized him by the throat with such ferocity and told him to shut up while presenting him the Cobra, Shimauma and Hasami bottles, ordering him to make sure those three won't learn of his true motive as he buys himself enough time to plan his final move.

Observing the "Build Annihilation Plan"
To his objection, Evolto's fellow Blood Tribe members took measures to personally see to the destruction of the Earth, an outcome which he no longer wished. To that end, "Kengo Ino" commenced the Build Annihilation Plan, compelling the populace of Japan, including Ryuga Banjo, to eliminate Sento. With the Cobra Fullbottle, "Kengo" combined the power's of Ryuga and the Blood Tribe to become Kamen Rider Blood. Evolto, however, intervened by retrieving Sento from defeat. Ultimately, the Blood Tribe trio were defeated by the four Kamen Riders, with their Lost Fullbottles being recovered by Evolto who voiced that their fates were sealed the moment they decided to betray him.

Endgame
"The sooner you reach the top...the more people you'll save. It's showtime!"

- Evolto addressing the riders the rules to their final battle. Days after the Blood Tribe's failed plan to kill Build, Evolto has had enough and finally schemed his final plan to purify the Castle and Hammer Lost Bottles. One day, Evolto, as Mido, reminisced on the Sky Wall disaster and how a war broke out due to utilizing the Rider System as weapons before the three regions of Japan became one again in a live broadcast at the Pandora Tower. Announcing the time has come for Japan to fall while laughing, Evolto abandoned his disguise and transformed into Kamen Rider Evol Black Hole, announcing his true name and origins, and then proclaimed he will destroy the Earth and absorb it throughout the entire country. However, he stated he has come to like this planet after living a decade among the denizens and offered a choice to save the Earth, which was directed to the Kamen Riders: bring the Castle bottle to the Pandora Tower the next morning, for their next battle shall be their last and the victor will determine the fate of the planet.

Later on, Evol, in a training room, fought against a digital Strong and Stretch Clone Smash, and easiliy defeated, so Utsumi could run a diagnostics on the Evol-Driver. After Ustumi announced no defects to his belt, Evol applaud him for being the perfect successor to Shinobu and expressed his excitement for the final battle. By morning, Evol emerged from the tower with a legion of Hard Guardians, approaching toward a crowd of people with several news station crews who fled in terror after the tower shot down a helicopter. As he asked the humans if they have a death wish, they broke down in terror and ran in all directions until Ryuga, Kazumi, Gentoku, and Sento approaching before him. After announcing their arrival, Evol asked if they have the Castle bottle, which Kazumi presented, and then Evol laid out the rules for their final showdown: the fight will be held at the top of the tower, and every ten minutes an area of Japan will be destroyed, which he demonstrated by creating a black hole over the sky on his left side, which engulfed a large portion of buildings and killed countless people before disappearing. As the riders became furious, Evol told them they should hurry if they want to save the rest before announcing the game beings now and taking his leave. Teleporting back to the top of the tower, Evol enacted the next stage of his plan as he removed his Evol-Trigger as he sat down, reverting to his Cobra form while splicing off a large sample of his own essence, which divided into copies of the Hokuto Three Crows and both Engine Bro's and Remocon Bro's.

From the top, Evol watched as the copies of the Three Crows attempted to assist the Kamen Riders, but Kamen Rider Grease caught on to his schemes by punching the Akaba copy, which morphed its arms into the Castle Hazard Smash's arm gauntlets. As Kamen Riders Build Genius, Cross-Z Magma, and Rogue wondered what was going on, Evol announced, through a megaphone-like style with the tower's power, that the Three Crows are copies created by his genes. Lying down while watching the Kamen Riders, Evol told them to hurry if they want to save the humans and the Earth. While Build, Cross-Z, and Rogue made their way up the stairs as ten more minutes passed by, Evol showed them a live broadcast of Grease, who remained on the first floor, being overpowered the three Hazard Smash copies before creating another black hole over a region of the city. Cancelling his transformation, Evolto watched as Kazumi lamented over his deceased friends before transforming into a new form: Kamen Rider Grease Blizzard. Evolto commented that Grease's new form will suit him for his imminent death before shifting the broadcast to Sento, Ryuga, and Gentoku, who've arrived at one of the tower's upper floors with Evolto's replicas of Engine Bro's and Remocon Bro's standing before them, which Gentoku remained behind to fiht them as he transformed into Kamen Rider Rogue.

Ten more minutes later, Evolto opened a black hole above a train tracks, consuming it and everything else close by before teleporting himself to the same room where Rogue and MadRogue, who revealed that he joined Evolto so he could avenge Namba, gain the second Evol-Driver, and input Evol's data in it to match his strength, was fighting the Engine and Remocon Bro's copies, which have merged to become Hell Bro's. After the Hell Bro's was destroyed by Rogue's Shark Charge Crush attack and MadRogue's Bike Evoltic Attack, which also purified the Hammer Lost Bottle the copies had on their person, Evolto reabsorbed the essence and commended Rogue and MadRogue for their fight before demanding the Hammer bottle. After they declined, Evolto transformed into Kamen Rider Evol Cobra and attacked both riders, easily overpowering them. After kicking Rogue aside, Evol took MadRogue solo as the latter revealed to him his true motive for his alliance, but Evol revealed he already knew and the input data will be too much for a human's body to handle as he knocked him to the ground. Turing around, Evol saw MadRogue access Evol's power by tapping into Phases 1 through 3, generating crimson and purple energy around him as he moved at hyperspeed, striking Evol multiple times before unleashing a crimson energy punch that drove Evol back. As MadRogue tapped into Phase 4, Evol became enraged and insulted MadRogue as both riders ran at each other until MadRogue's body bizarrely began to short out like a machine, which shocked Rogue and Sawa, who came with the Pandora Box and deliver the Shark and Engine bottles to MadRogue. The strange event allowed Evol to deliver a powerful punch, cancelling Utsumi's transformation and revealing malfunctioning circuitry in Utsumi's body, which Evol almost forgot that Utsumi was converted into a cyborg after Rogue shot him due to their plan to use Utsumi as a patsy for Faust almost a year ago.

Walking toward Utsumi, Evol stated his circuitry began malfunctioning as a result of replicating Evol's power before nudging the cyborg's body. As Rogue viciously attack Evol after realizing his actions from the Pandora Box's light stripped his former colleague of his humanity, Evol caught Rogue's punch and retaliated with an Evoltic Rider kick to Rogue's helmet, knocing him across to Sawa, who removed the Crocodile Crack bottle from Rogue's Sclash Driver and cancelled his transformation before his body began to disintegrate. Amused, Evol ran at Sawa and the injured Gentoku with his Steam Blade as he demanded the Hammer bottle, but Utsumi shielded them from Evol, taking the stab himself. Evol watched as Utsumi told the shocked Gentoku that he didn't do it for him, bu to protect the Lost Bottle before Evol removed his weapon from Utsumi's corpse and tossed it aside. Shaking the dead cyborg's bits off of his balde, Evol walked toward a horrified Sawa and Gentoku, who yelled in frustration as he grabbed his nebulasteam Gun and typhoported himself and Sawa to the top of the tower, leaving an unsatisfied Evol alone with Utsumi's body. Ten more minutes later, an untransformed Evolto opened another black hole in the sky over a city as he sensed his Hazard Smash copies were destroyed by a dying Grease and proceeded to the top of the tower as Sento, Misora, Sawa, Ryuga, and Gentoku heavily greaved over the deceased Kazumi. Evolto greeted them, but Sento, holding the Castle bottle, yelled at Evolto in fury as Kazumi's death was the alien's doing.

Final Battle & Death
"Earth's destruction is right around the corner."

- Evolto prepares himself for the final battle against the remaining Kamen Riders. With all three riders staring at him with malice due to Kazumi's death, Evolto reminisced of his time on Earth over the past decade and the events caused by the war and the Rider System while scolding the human race, which annoyed Ryuga. Focusing on the present, Evolto assured them that this day is the day for goodbyes and he'll take the Castle and Hammer bottles to obtain the ultimate power once again as he placed the Evol-Trigger and Evol-Driver on, and transformed into Kamen Rider Evol Black Hole while triggering the tower's power and teleported himself, the riders and the grieving Sawa and Misora to a forest. As Sento, Ryuga, and an injured Gentoku, who ignored Sawa's warning of not fighting in his condition, prepared to fight, they vowed to avenge Kazumi and transformed into Kamen Riders Build Genius, Cross-Z Magma and Rogue, running towards Evol as he unleashed red lightning at them. One by one, Evol fared well against the riders, easily overpowering Cross-Z and Rogue while matching Build at hyperspeed, sending the rider flying into Cross-Z with an upper cut, which forced Build to drop the Hazard Trigger. With all three riders lying on the dirt, Evol told them they can't beat him with those petty attacks as Build rose back up and engaged Evol, who was unaware that Cross-Z inserted Build's Hazard Trigger on his own Build Driver and activated the Overflow function.

Before Evol could counter, the powered-up Cross-Z forced Evol in the trees, overpowering him with a series of Volcanic Attack Rider punches before delivering a powerful blow that sent Evol flying through a tree. Siting up on the dirt, Evol commended Cross-Z's increased strength before stating his own strength has grown as well, due to his newly obtained emotions, and delivered an even more powerful punch to Cross-Z, sending him flying out of the trees. Evol spotted Rogue running at him with his Steam Blade and dodged the weapon multiple times while countering with his own assaults, stating he's not match for the alien rider as his body reached its limit with the lethal Nebula gas dosage, knocking the weapon from Rogue's hand and kicked Rouge out of the trees. Seeing Rogue's body beginning to break down, Evol told him he'll die before the day ends until Build tackled him, forcing him into the clearing before Evol overpowered him as he told the genius physicist that the Rider System was nothing more than an aid of the alien's resurrection, and proceeded to assault Build with hyperspeed attacks that sent the rider tumbling over the dirt and forcing him to drop the last two Lost Bottles. As he placed his foot on Build's hand to keep him from taking back the black bottles, Evol stated Build can't beat him with the Rider System before kicking him away. Evol then grabbed the two bottles and inserted them in the Lost Pandora Panel, turning them black and gold, and then performed the same method of absorbing the black panel through the Evol-Trigger's Feverflow function, transforming the alien into his Phantom State.

Stating he'll show them the worst to come, Evolto teleported the riders, Sawa, and Misora back to the Pandora Tower and teleported himself into space, opening a black hole that consumed the Earth's Moon, which in turn, increased Evolto's strength. Teleporting back to the tower, Evolto regained his Evolti Grasper gauntlets from consuming the Moon and told the humans to behave themselves as the Earth's destruction will begin before generating a crimson shock wave at Build and Cross-Z, knocking them to a pillar and cancelling their transformations. Biding them farewell as he activated his Black Hole Break, Evolto generated a large black hole over the Earth and it started to pull the planet in as the tear began to grow. Laughing as he sensed his power growing even further, Evolto praised himself for having no limits as he grew the Evolti Voider blasters on his shoulders and turned to the humans, telling them he loves to see despair on their faces and admired how their efforts had been in vain. Spotting Misora begging Vernage for help, Evolto became irritated and fired magenta energy beams from his Evolto Voider at her, but Rogue intercepted and took the blast, accelerating his body's breakdown as he fell on the grass. As Rogue rose back up and charged at the alien, Evolto grabbed his fist and told the former Faust leader he'll help him die before Rogue caught his arm, telling the alien he made a promise with Kazumi the night before: becoming his late father's successor as Prime Minster. Evol then knocked Rogue to the ground, but he rose back up and aimed for the Evol-Trigger while Evolto attacked him until he delivered an open palm uppercut that damaged the left side of Rogue's helmet, exposing his left eye. Evolto addressed the dying Rogue that he can't fare against him with his current Hazard Level, but Rogue told him he'll do what he can as his body's deterioration accelerated again, charging at Evolto who took his punch before he knocked him down again.

Evolto attempted to kick Rogue, but he caught his leg and began punching the Evol-Trigger multiple times before kicking him. The dying rider, however, kept aiming for the trigger as Evolto pummeled him with all his might to the point of making Rogue dizzy, seizing by his suit's collar and kneed him before tossing him. Seeing him rise again, Evolto attempted to punch Rogue as he aimed for the trigger, but was shocked to see that the hit caused damage. Evolto then found himself being forced back by the dying Kamen Rider's attacks, sensing his Hazard Level increasing as Rogue continued his assault. Faltering back, Evolto wondered how his strength increased as Rogue executed a Crack Up Rider kick that connected, even when Evolto launched a crimson energy ball at Rogue, which failed. The kick connected and the crocodile jaw energy crushed Evolto's body before he summoned enough strength to dealt a critical blow to Rogue, sending him crashing into a pillar and cancelling his transformation before his body completely disintegrated. Scolding Gentoku's sacrifice, the injured Sento and Ryuga rose back up, which Evolto asked if they increased their own Hazard Levels by their anger, but Sento assured him a Kamen Rider gets his strength from hope. As they transformed into Build Genius and Cross-Z Magma, dealing more damage to their bodies, Evolto attempted to engaged them, but found himself unable to move as he looked down to see the Evol-Trigger damaged. Attempting to move, Evolto saw Build execute a Genius Finish Rider kick and attempted to block it, but failed as the kick dealt a critical blow. To Evolto's shock, the black Pandora panel painfully came out of his body, paralyzing him as he saw Cross-Z ran with a strange white panel and placed it on the black panel, merging with it as it caused a feedback that blew away Cross-Z. Before Evolto could react, Build severed the energy tendril holding the panels with his Fullbottle Buster, cutting Evolto off from the warping power.

Evolto then saw Misora run to the center of the ground with the Pandora Box as Build took the white panel, which absorbed the black one and took the Lost Bottles, and placed it on the box, activating its power that shot a rainbow energy beam, that was being fed by the Genius Fullbottle's energy, at the black hole. Before Evolto's eyes, he saw the beam dragging a duplicate of the Earth from the black hole before the energy from the Genius bottle was completely drained, reverting Build to his TankTank form as the empty bottle replaced itself with the HAzard Trigger and FullFull RabbitTank bottle. Turing to Build and Cross-Z, Evolto demande to know what was going on, which Build told the alien they're enacting Shinobu's plan: merging their world with a parallel Earth that has no Sky Wall to create a brand new Earth without him by using the alien's power to complete the fusion. Gesturing to a tear in the beam, Build told Evolto they're going to throw him in as he lunged at the alien, but both Evolto and Build were shocked when Cross-Z took the FullFull RabbitTank bottle and deactivated Build's transformation. Cross-Z told Sento that he has Evolto's genes within him and it's better for him to die with the alien as he seized Evolto and thanked Sento for everything before using his power to fly toward the beam's opening. Evolto attempted to free himself, but failed as both he and Cross-Z entered the light.

However, Evolto was able to absorb Cross-Z as they landed on the alternate Earth. Anticipating Build to rescue Cross-Z, Evolto morphed into Ryuga and pretended to be unconscious until Sento, as Kamen Rider Build RabbitRabbit, arrived from the light tear and approached him, which Evolto rose up and began attacking Build. After Build dodged all of his attacks, Evolto reverted back to his Ultimate State form and told Build he absorbed Ryuga to restorer the Evol-Trigger before stating he will consume the rider as well in order to completely repair the device. Evolto then engaged Build, stating the plan to merge both planets can't come to fruition without his own energy and that he'll let both planets collide with one another as he overpowered Build, who refused to be deterred. Standing still as Build's attacks did nothing, Evolto sent him flying with a powerful punch as he mocked Build for not being able to match him without the Genius Bottle before dealing critical blows, cancelling Build's transformation. Evolto morphed into Soichi as Sento laid on the sand exhausted and injured, telling the human he's a nobody that shouldn't exist in the planet, which infuriated Sento, forcing him to rise and strike Evolto, but he caught the human's fist and twisted it. Evolto then mocked Sento by stating if he hadn't built the Rider System and triggered the events leading to Japan's civil war, none of this would've happened, and the alien told Sento he's just a fake hero of his own design before blasting him away with a crimson shock wave. Turing back to his Ultimate State, Evolto bid farewell to Sento as he prepared to kill him, but was shocked to find himself becoming paralyzed as blue electricity came out of his body, and to hear Ryuga's voice coming out from him. Struggling, Evolto heard Ryuga tell Sento he is a true hero, irritating the alien to the point he regained control of his body and silenced Ryuga, who managed to force the Dragon Fullbottle out of Evolto's body, which turned silver again as it landed in front of Sento.

Stating he's sealed Ryuga, Evolto prepared to finish Sento, who regained his confidence and vowed to save Ryuga as he transformed into Kamen Rider Build RabbitRabbit. As both riders engaged one another, Build acknowledged that the alien did make him a Kamen Rider, but it was Build's friends that he fights for justice, they helped him create Sento Kiryu and Kamen Rider Build, and that he'll use justice to create a new world and fill it with love and peace, but Evolto yelled destruction is true power and he'll destroy Build's justice as they both run at one another. As the tear began to slowly close and the planets started to disintegrate from the energy, Evolto forced Build to the ground and ferociously pummeled Build enough to begin his body's breakdown, but Build transformed into his TankTank form and dealt damage to Evolto with the treads on his Fight Might Gauntlets, which caused Evolto's body to breakdown as well. Stating their final battle will determine who will die first, Evolto kicked Build and viciously slashed him with his gauntlets, accelerating his body's breakdown until he transformed into Build RabbitTank Sparkling, leaping forward and dealing a powerful kick to Evolto, accelerating his breakdown as he lost his Evolti Voider blasters. Faltering, Evolto blocked Build's shots from his Hawk Gatlinger, knocked the weapon aside before kicking Build, who managed to rise back up and strike with his Drill Crusher, but Evolto shoved it aside and dealt a powerful punch to Build, costing the alien his Evolti Grasper gauntlets. Infuriated, Evolto ran at Build and struck him, which reverted the rider to his RabbitTank Best Match form as his body's breakdown accelerated again. Seeing Build in his base form, Evolto, exhausted, stated the victor has been decided, but Build said they'll see as the Rabbit Fullbottle turned gold.

"You...destroy me? That won't happen! You damn human!"

- Evolto's final words before his death.

As Evolto saw the transformation, Build summoned his Fullbottle Buster and inserted both the gold Rabbit and silver Dragon bottles in the weapon, but Evolto laughed and stated it won't work as Build moved forward, but jumped at the last second and struck Evolto with a Just Match Break Rider slash three times, stating that he and Ryuga are the best combination. His body's disintegration accelerating, Evolto attempted to run, but found himself paralyzed once more as Ryuga surface again, allowing Build to transform with both biotic bottles into Build RabbitDragon Trial form. As Build leaped up to execute a Vortex Attack Rider kick, Evolto managed to execute a FeverFlow Evoltic Break and leaped up, but Build's kick struck him first. Descending from the air by Build's kick, Evolto saw Build revert back to his RabbitTank form as the alien felt his body's breakdown accelerating even further. As Build stated this is the end, Evolto found it impossible for him to be defeated by a human and cursed Build before his attack fully connected, killing the alien with enough force and unleashing his power, allowing the parallel Earths to merge with each other.

Kamen Rider Build NEW WORLD: Kamen Rider Cross-Z
It is later revealed that a piece of Evolto attached itself to Ryuga Banjo when the worlds merged, allowing Evolto to live on in the new world. When Killbas appeared and attacked Ryuga, Evolto emerged as Blood Stalk and engaged him, before escaping with Ryuga and the Pandora Box.

After Killbas was defeated, Evolto left Ryuga's body and departed.

Personality
"With Kamen Rider Build defeating evil monsters...Misora was able to purify the Bottles, thinking she was doing it for justice. In other words, that was all you existed for. You were merely acting the hero of justice. You were just playing Kamen Rider."

- Blood Stalk unveiling his manipulative persona to Sento "Soichi"'s persona as nascita's owner is an enthusiastic but laid back man who paternal demeanor served as a gentle guidance to Build's team. While he appears to have some genuine sentiment for this makeshift family, Evolto made it clear that he sees all of them as means to an end.

As Blood Stalk, he is a self-proclaimed strategist. He also seems to have a lot more of an unperturbed and sinister attitude compared to the more focused Gentoku, nonchalantly fooling around even when doing his job as a Faust enforcer. Such is seen when instead of directly engaging Build, he was casually laying back and letting the Square Smash do most of the fighting until it was the right time for him to interfere by making the Smash grow. He also dislikes taking orders from anyone, preferring to do things his own way.

Evolto also viewed his battles with both Sento and Banjo as an experiment to measure their Hazard Level. He was visibly entertained when both of them had a rise in their Levels and gave them hints in return. He isn't even bothered by opposing Gentoku temporarily to let them escape so he can see how strong they become.

Evolto can be cruel and ruthless if he wants to, making him not much different from Gentoku in regards to their aggression. He is more than willing to commit more heinous acts, such as killing several Touto guards using his venom, and changing Eita Kawai's face into that of Shingo Kuwata just to show he could. Like Gentoku, he views science and the Rider System as instruments for war. Evolto has the traits of a high-functioning sociopath, with his true intentions of destroying the Earth using the Pandora Box coming to light, and his tendency to betray those he comes across with. He manipulates both heroes and villains alike to further his twisted genocidal quest and he has no qualms killing them once they served their purpose.

Once he opened the Pandora Box, completing the Pandora Tower and claiming an incomplete Evol Trigger, Evolto becomes more intent on achieving his initial goal (destroying Earth) as soon as possible. He also becomes more short-tempered, irritable, and temperamental since the Riders and Vernage continually ruin his plans. This wrathful tendency is rooted with his overinflated pride; and when his ego is bruised, Evolto will go in petty lengths in making the Riders suffer, only for them to counterattack even more. Evolto's excessive opinion of himself does more harm to him than benefiting his goals. After Evolto personally killed Namba and gained a mentally broken Utsumi's loyalty, Evolto now planned to rule the Earth instead of destroying it and become laid-back once more after achieving his perfected form, Evol Black Hole.

After Sento, as Build Genius Form managed to neutralize some of Evolto's Nebula Gases, Evolto now could understand and feel human emotions. This resulted in him becoming ecstatic, fierce and allow Evolto to feel rage and hatred towards Sento.

Evolto true nature is shown after he get his Phantom State. He view humans as nothing but an inferior life form as he tends more to look down on Team Build and get irritated easily when things don't go exactly like his plan. He also resumes his original goal to destroy Earth once more, this time fueled by pure hatred towards Sento and Team Build as they somehow manage to ruin his plan every time. Because of this, he is somehow started to view humans in different way, even goes far by mocking Killbas before his demise, saying "Because of human that is" when Killbas unable to accept his defeat from Banjou

Evolto has a tendency to sprinkle bits of Italian in his speech, most commonly saying "Ciao" as a goodbye, which in turn would eventually be one of the phrases announced in the Evol-Driver after a Evoltech or Black Hole Finish is performed.

Powers and Abilities

 * Host Possession: Evolto can possess any living being to carry out his plans to destroy all living planets he comes across, He is able to wait dormant in the Pandora Box until another living being finds it, at which point, he leaves the Pandora Box to possess whoever discovered it. After achieving Black Hole Form in recent episodes, he apparently no longer needs a host for a body to survive, yet he still uses the appearance of Soichi Isurugi for personal preference. He can also use a portion of his own DNA to possess others separately, either to ensure his continued survival, or to do his own bidding.
 * Computer Proficiency: Evolto has some level of programming knowledge, as he was able to hack the GPS on a stolen motorcycle, and steal the completed Sclash System data from Sento's computer.
 * Altered Physiology: Being the first human to be exposed to the Pandora Box, "Soichi" has demonstrated numerous superhuman abilities since his return from Mars. Unbeknownst to everyone, including Soichi himself, these powers came from the Evolto.
 * Hazard Level 5+: Due to Evolto being an extraterrestrial being, he is able to achieve a Hazard Level of 5, thus allowing him to use the Evol-Driver.
 * Matter Reshaping: Evolto was able to manipulate a tablet computer into a rod shaped item that he used as a back scratcher.
 * Superhuman Agility: Evolto was shown to be able to leap at a scale far beyond human capacity after his battle with Build's RabbitTank Sparkling Form.
 * Isurugi switching face.pngIdentity Manipulation: Using a cloud of steam from his hand, he can make anyone's face look like anyone else's; the process seems painful to those who are awake to feel its effects. While the permanence of the change is yet unclear, certain individuals have been shown to retain their new identities for more than a year. Initially thought to be an ability of the Blood Stalk system, this power has since been revealed to be Evolto's. However, it was shown that this power could be applied only if the copied person is dead or killed. This process also seems to have an effect on the subject's physiology as well, as seen when Juzaburo Namba discarded his walking stick and no longer needing glasses to see upon having his appearance changed into that of the dead Masakuni Mido. This process has also been demonstrated to be reversible at Evolto's discretion.
 * Isurugi memories wipe out.pngMemory Manipulation: Evolto has shown the ability to erase the memories of others with nothing more than a touch of his hand. Unlike the amnesia induced by Nebula Gas, Evolto's memory manipulation is shown to be complete, causing a total wipe of the person's previous identity. However, with time, some victims have shown to be able to recover partial memories, skills, or even the entirety of their past given proper circumstances.
 * Pyrokinesis: Evolto could shoot a crimson flare from his hand or with his Transteam Gun at the enemy. Its power is enough to destroy Banjo's Dragon Sclashjelly and Sclash Driver. He is able to use this power in both his civilian form and as Blood Stalk, later also carried after he becomes Evol.
 * Pandora Box Control: Evolto could manipulate Pandora Box power to do his bidding, either to attack enemy with various phenomenons or to change Pandora Tower inner structure.
 * Superhuman Speed: Evolto is shown to be able to move at speeds faster than the human eye. He demonstrates this ability by escaping with the Box after defeating Build, and at the nascita where he knocks everyone out. He gains this ability after possessing Ryuga.
 * Instantaneous Transportation: Evolto is shown with the ability to teleport him (or either others he wishes) to different locations. He was able to bring everyone at nascita to the center of Pandora's Tower instantly.
 * Human Disguise: After reaching his fourth Phase, Evolto gains the ability to assume a human form, namely that of his former host, Juzaburo Namba, and even Masakuni Mido.
 * Dagger Proficiency: Although a very subtle example, Evolto is capable of throwing knives at a high precision rate.

Weaknesses

 * Vernage: Vernage's powers are able to neutralize those of Evolto's. Sento Kiryu made use of this knowledge and used Build Genius Form to transfer Vernage's essence into Ryuga Banjo, so as to prevent Evolto's DNA within Banjo from causing him to go berserk again.
 * Evol-Trigger: Evol's upgrade device is also his primary weakness; when the Transcendence Meter on the Trigger is struck forcefully with an attack, it will paralyze him for a period of time whilst reverting him back to Cobra Form. This weakness is carried over to the Hazard Trigger. Additionally, as shown in The Scientist of Hope, Evolto is unable to use the Evol-Trigger if he is not a complete being, leaving him to choose between fighting at his strongest or having a backup contingency plan should he fall in battle.
 * Superiority Complex: This is Evolto's fatal flaw. He has an over-inflated opinion of himself as a "higher lifeform". When he is defeated by those he deemed inferior, Evolto quickly responds to anger and will go to great lengths seeking payback, but in the process he loses his cunning and pragmatism, giving his enemies an opening to strike back.

Devices

 * Transteam Gun - Blood Stalk's transformation device and personal weapon. Evol inherits it as his personal weapon
 * Fullbottles - Blood Stalk's transformation trinkets. Used by Evol to summon weapons and perform finishers.
 * Evol-Driver - Evol's transformation device
 * Evolbottles - Evol's transformation trinkets
 * Fullbottle Holder - Carrier strap for Evol's Evolbottles
 * Evol-Trigger - Evol's upgrade device for Black Hole form

Weapons

 * Steam Blade - Blood Stalk's standard sidearm weapon. Can combine with the Transteam Gun to form the Steam Rifle. Continued to be used by Evol.
 * Drill Crusher - Evol's personal weapon in Rabbit Form. It is also used in Black Hole Form when played in Ganbarizing.
 * Beat Closer - Evol's personal weapon in Dragon Form, and as Blood Stalk, loaned from Cross-Z Charge.
 * Hawk Gatlinger - Evol's weapon granted by the Gatling Fullbottle

Portrayal
Evolto is voiced by Tetsuo Kanao (金尾 哲夫), who previously voiced Namakelder in Happiness Charge Pretty Cure!. As Blood Stalk and Kamen Rider Evol, he is portrayed by suit actor Kazuya Okada (岡田 和也) regardless of the body he possesses.

While possessing or impersonating others, he is portrayed by their respective actors.
 * While possessing and later impersonating Soichi Isurugi, he is portrayed by Yasuyuki Maekawa (前川 泰之)
 * While possessing Ryuga Banjo, he is portrayed by Eiji Akaso (赤楚 衛二)
 * While possessing Sento Kiryu, he is portrayed by Atsuhiro Inukai (犬飼 貴丈)
 * As Juzaburo Namba, he is portrayed by Akira Hamada (浜田 晃)
 * As Masakuni Mido, he is portrayed by Norimasa Fuke (冨家 規政)
 * While briefly possessing Kazumi Sawatari, he is portrayed by Kouhei Takeda (武田 航平)
 * While briefly possessing Nariaki Utsumi, he is portrayed by Yuki Ochi (越智 友己)

Etymology
'Evolto' and 'Evol' are both taken from the English words 'evolution' and 'revolt'. 'Evolution' also sounds similar to 'revolution', which is used liberally in Evol's Black Hole Form announcements.

Appearances
Эвольт