Cyclone-Accel Xtreme

CycloneAccelXtreme is a form that is only described by Shroud as being the ultimate form that can be attained by Kamen Rider Double. Rather than being a union between Shotaro and Philip, CycloneAccelXtreme is the union of Ryu Terui and Philip, as both of their physiologies make them immune to the attacks of the Old Dopant and the Terror Dopant. Shroud states that Ryu's hatred and rage is needed for Double to fight at its full potential. However, Ryu decides not to fight as part of this form after showing Shroud that they can fight with compassion rather than hatred. Though not making a physical appearance in the series, CycloneAccelXtreme appears in Kamen Rider: Climax Heroes OOO where he is armed with both the Engine Blade and the Prism Bicker. While able to use the Engine Blade's Gaia Memories in his attacks, CycloneAccelXtreme uses the Prism Memory's ability to link Philip's three elemental Gaia Memories with the Accel Memory to perform his own version of Bicker Finallusion.