Eubulon

Eubulon known as the "Advent Master", is the creator of the Kamen Riders from the Planet Karsh.

Backstory
He and General Xaviax are from the Planet Karsh and Xaviax was the leader in their north army, while Eubulon Developed weapons for him in their war against the south. Although the North won, Karsh was turned into a waste land and Eubulon was enlisted to create a transportation device to send a mass amount of people from other planets as slaves to rebuild their world, starting With Ventara. When he arrived, he fell ill and almost died. He was taken in by a Ventaran family who helped him recover and this helped him realize that he couldn't enslave a peaceful planet. He soon told Xaviax that he wouldn't take the Ventarans and that they would have to find another way to save Karsh. Unfortunately, Xaviax refused to listen, leading him to think that Eubulon had committed treason and he decided to enslave Ventara Himself. Eubulon warned Ventara's leaders of what was coming and then created the Kamen Riders to stop Xaviax, while the Ventarans selected twelve of their very best to take up the mantle. Eubulon also created his powers just for himself and has the ability to change the DNA sequence of the Rider Decks so anyone can use it. He fought Xaviax to a draw and ended up being found on Earth in Roswell, New Mexico. He warned the No-men of Xaviax upon his arrival but was injured badly and was unable to tell them anything else.

Reawakening
60 Years Later, Len was brought in to reactivate Eubulon. Len had informed him about Adam's betrayal and of Xaviax's activities. With Xaviax on the move, he reassigns the Siren deck to Maya as she helps Len stall Xaviax as Eubulon goes to retrieve the Riders in the Advent Void. He manages to bring the Ventaran Torque, Strike and Axe (named Chance, Price and Hunt respectively) as he and Len explain their current situation to them. He gives them a device that will upload a virus in Xaviax's transportation devices as they will need some of them to retrieve the people of Ventara. Eubulon goes back to the Advent Void to retrieve other Riders, including Kase and Kit. When he brings them out of the Advent Void, he gives Kit the Onyx deck to help out Len, Chance and Price. After returning to the No-Men's base, he begins repairing the key in order for it to fully function again, before sensing Maya in danger and sending Kit to assist her.

When he senses Kit and Adam fighting each other, he interrupts their battle in order to hear out Adam's side of the story and prevent Kit from giving into anger. He brings Adam back to the base to hear him out, but the other Riders aren't interested. Len leaves the base but Eubulon follows him and manages to have the others trust Adam, if only slightly. He goes with Price and Hunt to locate another transmitter, but they have a difficult time searching for it. After being ambushed by monsters Eubulon retreats when Hunt gets injured. He begins to heal Hunt when they return to base.

Eubulon, while meditating, is sought out by Kit and Maya who ask him of the origin of the Kamen Riders. He tells them that he's from Karsh like Xaviax, as well as their planets history and about the creation of the Kamen Riders. Eubulon adds that because he invited the teleportation transmitters, it'll be his fault if Xaviax wins.

Later, Eubulon discovers the reactivated transmitters. When Adam and Len return, Adam tells what happened to him and Eubulon explains that he would never do something like that, leading Kit to realize that it was a trap set up by Xaviax. He sends the Riders along with Trent and Maya to Xaviax's base and hands them each a Link Vent card which, when used by all 13 Kamen Riders, will combine all 13 Final Vents and unleash it into one devastating attack. When the Riders destroy the shield generator, Eubulon manages to stop Xaviax right before he activates his transmitters. The evil General berates The Advent Master for "abandoning His own people" on Karsh, but Eubulon justifies it by saying that Xaviax destroyed their planet through war and he couldn't let it happen to another. He also adds while that their species time of existence is done, humans still have a chance of survival. Xaviax becomes even angrier at this and says that Karsh and Its people are superior above all others and won't let anything, including Eubulon cause their race to die out. This leads to a battle between the two of them with Xaviax gaining the upper hand. Eubulon is then saved by the two dragon Riders who, along with Len and Kase, distract Xaviax long enough for him to bring the remaining six Riders back from the Advent Void. Soon enough, all 13 Kamen Riders use their Link Vents and destroy Xaviax once and for all. Eubulon states that their work is far from finished and together with the other Riders, he manages to bring back the people of Ventara.

During the Epilogue, he rescues all of the other earth riders and wipes there memories of them being riders. He even cured Chris of his asthma and most likely cleared Brad of his cheating scandal and brought Vic out of his Coma. He also separates and retires Adam from the Dragon Knight deck and gives it to Kit Taylor, who has officially become Kamen Rider Dragon Knight. Using his technology, he continues to help rebuild Ventara and continues to assist the Kamen Riders from any more evil that may threaten Ventara and Earth.

Abilities
Eubulon, being the creator of the Kamen Riders, has the ability to manipulate the rider's arsenal. He can change the DNA lock each deck has and reassign it to other people if necessary. He also has the key to the Advent Void, which he created as a fail safe to prevent any Rider from getting killed in action. While the key was damaged with his fight against Xaviax, it still functions well thus making any future vents a non-issue, but as it was damaged, he had to begin repairing it after retrieving only a small handful of Riders. If he ever needs to defend himself, he can use the key to transform into his Rider armor.

The key can also be used as an Advent Deck while in his Rider Form and includes a different card slot format than the others. With his reappearance, the war against Xaviax has changed from a fight for survival to a fight against time. He also creates a new Advent Card called Link Vent and gives it to all 13 Riders. This card, which design looks like Strike's Unite Vent, combines the power of all 13 Final Vents and unleashes it into one condensed attack. This card was specifically made to destroy Xaviax as he had proven to be more powerful than expected.

Rider Statistics
Ability Perimeters
 * Height: 190cm
 * Weight: 93kg
 * Maximum Running Speed: 100m/4.5s
 * Sight: 20km
 * Hearing: 15km
 * Maximum Jump Height: 50m
 * Punching Power: 300AP
 * Kicking Power: 450AP

Advent Deck
Eubulon's slot works very differently than the other Kamen Riders. Unlike the others, his is a swipe-based card reader (located on his right arm) and when swiped, the card burns up (though this may just be due to the fact it was actually Xaviax shape-shifted into the form of Eubulon and copying his powers at the time). In addition, his cards are horizontally designed unlike the other Riders, whose cards are designed vertically. Eubulon never actually uses his cards. They were only used in episode 36 by Xaviax in Eubulon's form when he confronts Adam, though It's assumed that Eubulon has these cards since his Advent Key also acts as an Advent Deck.
 * Sword Vent: Conjures a spiked blade like lance that can shoot blue fire.
 * Speed Vent: Accelerates Eubulon to high speeds.