The dimensional rift is the space in between the A.R. Worlds, which are traversable via an Aurora Curtain. The dimensional rift itself appears an otherwise empty space filled with a purple mist, a one might confuse it for Hell.
In Super Hero Taisen, the vast majority of Kamen Riders and Super Sentai are respectively sent to the dimensional rift, under the pretense of being defeated, by Gokai Red and Kamen Rider Decade. Indeed, upon "killing" their enemies, Marvelous and Tsukasa's respective weapons appeared to emit the same purple mist found in the dimensional rift, which is seen to envelope their targets before vanishing them.
Backed by the might of Dai-Zangyack, Marvelous attacked Amanogawa High School to draw out Kamen Riders Fourze and Meteor. Though he nearly defeated Fourze, Marvelous was interrupted by his fellow Gokaigers, to whom he explained the conflict between the Sentai and Riders. Following this, after having Rider Hunter Silva wear him down, Gokai Red "killed" Kamen Rider Meteor while Fourze was forced to fall back amidst the firepower of the Gigant Horse.
Soon after, the other Gokaigers went to confront Decade, who was engaged against the Go-Busters, their successors. However, they were beaten back by the forces of Dai-Shocker, with Decade using the opportunity to "kill" Gokaigers Yellow, Pink and Gokai Silver. The Go-Busters fell back amidst the assault of the Crisis Fortress, while surviving Gokaigers Blue and Green likewise fled.
Kamen Rider Diend, Daiki Kaito, an old friend and rival of Decade, confronted Gokai Red but was quickly overwhelmed. Meanwhile, Eiji Hino, Kamen Rider OOO, was fighting Dai-Zangyack forces with his allies, Birth and Birth Prototype. After "killing" the two Births, Gokai Red attempted to finish off Diend but was stopped by OOO, who sacrificed himself to protect Diend. Kaito made his escape with Hina Izumi, a friend of OOO's, and the two soon came across the surviving Gokaigers, Joe and Don.
When Joe remembered the word from Marvelous that the late Akarenger knew the true story, Daiki arranged for their party to be picked up by the time travelingDenLiner, which delivered them to meet Akaranger of Winter 1976. Returning to the present of April 21st in 2012, Akarenger was joined by the five surviving Sentai: Goggle V, the Liveman, the Zyurangers, Megarangers and the SWAT ModeDekarangers. Immediately after they were confronted by what appeared to be Kamen Rider 1, leading the surviving five Riders: Kuuga, Faiz, Kabuto, Kiva and Double on their respective Rider Machines. In the ensuing deciding battle, Akarenger and Rider 1 wiped out the other's allies before attacking each other. It was at this point that they revealed themselves respectively to be Gokai Red and Decade in disguise.
Finally, Marvelous and Tsukasa, seemingly forsaking their comrades, respectively "killed" Joe and Kaito with their swords, leaving only themselves as well as Don and Hina. Joe and Kaito found themselves in what they first assumed was hell, only to be proved otherwise when they encountered the fallen Gokaigers and Eiji Hino, the latter of whom informed them that the real battle was about to begin.
Ultimately, all the Kamen Riders and Super Sentai, whom had been presumed to be wiped out, returned from the rift via the dimensional walls as Tsukasa and Marvelous revealed their ruse to defeat the Shocker-Zangyack Alliance.
Curiously, a flashback shows G3, Knight, Zolda and Gatack among the Kamen Riders "defeated" by Gokai Red. However, they are not seen to reappear for the final battle.
Similarily, the Gekirangers are seen in a team of five, including GekiViolet and GekiChopper, when they are "defeated" by Decade. Though the additional heroes are seen to participate in the final battle, they were not seen returning through the dimensional wall beforehand.
Of the Kamen Riders featured in the film, the Kamen Rider Den-OTaros quartet were spared Captain Marvelous' hunt. Indeed, as residents of the time travelingDenLiner, commanded by the Owner, they are present as the DenLiner drops Daiki, Hina, Joe, and Don in Winter 1976 to catch up with Akarenger, actually Captain Marvelous in disguise. Despite this, Momotaros, as Den-O Sword Form, is later seen returning through the dimensional wall with the "defeated" Kamen Riders. More confusingly, his fellow Taros Imagin are seen to fight alongside him in their respective Den-O forms during the final battle, despite not being seen to accompany him earlier.
Kamen Rider Fourze, unlike Meteor, and the three Go-Busters, as the then incumbent heroes, were not explicitly shown to have been sent to the dimensional rift. Infact, they are seen under fire from the respective "evil fortresses" of Dai-Zangyack and Dai-Shocker before abruptly disappearing for a significant portion of the film. While the Go-Busters and Fourze eventually reappear alongside Meteor, before the previous heroes return through the dimensional wall, their activities during the interim remain a mystery.