Adam

Adam is the original Kamen Rider Dragon Knight, and therefore Kit's Ventara counterpart, who betrayed the other Kamen Riders venting them while in suspended animation (save for Kase and Len) in order to help Xaviax take over Ventara. Adam wanted to retire from being a Kamen Rider after Eubulon disappeared, which Xaviax promised to do after venting the other Riders. Not wanting to fight anymore after betraying his fellow Riders, he secludes himself with Sarah in an illusion created by Xaviax until he is called upon again after all the Riders but Len are vented.

History
Like the Earth Riders, he was tricked by Xaviax but since then, his betrayal weighed heavily on him. In order to keep his secret safe, he is assigned to befriend Len and Maya, who is the temporary Siren, and keep them from destroying more of his devices. He destroys a monster attacking Len hoping to get back his trust saying that Xaviax had tricked him. But Len is not easily swayed as both trigger their Survive Modes. Adam attempts to use his Final Vent in retaliation but runs away.

Following the return of three of his fellow Ventaran Riders, he tries to gain back the trust of Hunt, Kamen Rider Axe, who threatens to vent him following a battle against Xaviax's monsters. Xaviax, fed up with his failure to infiltrate the Riders, sends monsters to attack Maya which Adam attempts to save. He later meets up with his mirror twin Kit Taylor who berates him for betraying the other Riders. Adam argues that Xaviax tempted him with something more important than Kit's offer.

This explodes between a battle between the two mirror twins as Kit, as Onyx, fights Adam and overpowers him until Eubulon shows up. Eubulon allows Adam to explain why he betrayed the other Riders but the others are not interested in what the traitor wants to say. Eventually, Adam does prove his worth and helps the other Kamen Riders stop Xaviax. After the final battle with Xaviax, Adam decides to retire from being a Kamen Rider, and Eubulon gives his Advent Deck to Kit.