KAMEN RIDER DRAGON KNIGHT

While searching for his missing father, Kit Taylor finds an Advent Deck - a special card deck that allows the carrier to transform into a Kamen Rider and utilize unique weapons and powers - and uses it to become Kamen Rider Dragon Knight. He butts heads with Len, who serves as Kamen Rider Wing Knight, but the pair join forces after Kit learns that the wicked General Xaviax has imprisoned his father and is using him and the other humans that his monsters abduct to gain power and rebuild his homeworld. In addition to training Kit to fight like a Kamen Rider, Len tells Kit all about the twelve Riders who banded together as the protectors of Ventara - a mirror world opposite to our own - to take Xaviax down. However, due to the traitorous actions of Kit's predecessor, the original Dragon Knight, General Xaviax destroyed most of the Riders via a process called Venting - which traps defeated Riders in the "Advent Void" between dimensions forever - and stole their Advent Decks. Furthermore, Xaviax has also begun using his shapeshifiting abilities to coerce humans into joining him, giving each one an Advent Deck and the corresponding Kamen Rider powers, with which they fight to eliminate Kit and Len.

Taken from Wikipedia.