Read more about Kamen Rider Siren at: Wikipedia

Official Site: Adness Entertainment

The characters of Kamen Rider: Dragon Knight are very varied. They include the inhabitants of the Earth, the monstrous inhabitants of the alternate dimension Ventara, and the Kamen Riders who can exist in both.

Created by the "Advent Master" Eubulon, the original 12 Kamen Riders were the chosen defenders of the "mirror world" known as Ventara. With the exception of Wing Knight (and later Siren), they were all implied to have been killed (referred to as being "vented") in battle with Xaviax when one of their own (the original Dragon Knight) betrayed them and their Advent Decks were stolen. Since the Decks were designed to work with only one person, each deck only functions again when given to humans on Earth that are "mirror twins" of their Ventaran counterparts, with matching DNA or when Eubulon reassigns the deck. To access the powers, the chosen deck wielder holds the Advent Deck carrier in front of them to activate a burst of energy that creates the Advent Belt holder for the deck while calling out the words "Kamen Rider". The deck is then inserted in the belt and spins, further activating a pair of rings that surround the bearer and creates the armor for the specific Kamen Rider. The energy emitted from those rings can be used to repel others away while transforming. Each Kamen Rider has a special sense that can detect Mirror Monsters and other Kamen Riders and, in some extent, their condition. The decks also give the Riders the ability to travel from one place to another instantly by traveling through any mirror or reflective surface and traversing the mirror world to end at their intended (or at times unintended) destination(s), be it in their Rider armor or human form. They can also travel with other humans or push them through a reflective surface to the other world as long as they keep in contact with them while traveling. If either side of the mirror is blocked or destroyed, they cannot travel through that mirror. Riders usually travel through the dimensions with a specialized motorcycle parked in between the dimensions called an Advent Cycle. A Rider may also travel with their own motorcycle which, upon transforming, will change the motorcycle's appearance as well.

The Kamen Riders will be assisted by their own Advent Beast (Contract Monsters in the video game). A Rider starts off at a blank form, a colorless, generic armor with limited abilities and lack of any real power. Once a Mirror Monster is confined via their contract cards, it forms a Contract with the Rider who captured it. This changes the Rider's armor, abilities and Advent Cards based on the Advent Beast confined. The Advent Beasts support their human partners through the Advent Decks, usually appearing when an Attack Vent or a Final Vent is used. Should a Rider become vented, their respective Advent Beast remains in the deck, as Xaviax presented all but three of the decks to the Earth Riders with the decks still active and with the insignia displaying their beast still on them. The lone exception to this was Kit, whose Advent Beast was not present in the deck when he found it. When each of the Riders was vented, their decks remains in the activated state. Maya who gained Kase's Advent deck temporarily, did not have to locate and then form a contract with her Advent Beast despite the deck being reassigned to work with her DNA

Because of the nature of the contract, once it is established, a Rider cannot simply quit being a Kamen Rider because as Len describes it, it constantly calls Riders back to fight monsters and protect the people and only Eubulon can unlock the decks. Also Riders experience a phenomenon referred to as the rage of the Advent Beast which, if left untamed, can give a Rider nightmares.

Kamen Rider Siren has not been a contender in any CBUB matches.