Kamen Rider Yuuki

The movie Saraba Kamen Rider Den-O: Final Countdown introduces a new system, Kamen Rider Yuuki (仮面ライダー幽汽), an evil Kamen Rider system used by those who have control over the Ghost Train (幽霊列車), a skull-faced steam-engine that transcends the world of the dead and the flow of time. The Gaoh-like armor has an aged appearance, with rust and numerous scratches dotting its surface, keeping with the overall theme of death along with elements of the samurai and steam trains.

Skull Form
Skull Form (スカルフォーム) is the form of Yuuki that is accessed when Ryotaro Nogami is possessed by the Ghost Imagin. In Skull Form, Yuuki's Full Charge is the Terminate Flash (ターミネイトフラッシュ) using the sword of the Ghost Imagin. As the name and design implies, Skull Form's motif is the skeleton.

Hijack Form
Hijack Form (ハイジャックフォーム) is the form of Kamen Rider Yuuki that Shiro accesses on his own. Hijack Form has a black and red color scheme, compared to Skull Form's black and gold color scheme, lacking the skull-theme. Hijack Form also performs the Terminate Flash, but does so with his Savage Gasher (サヴェジガッシャー) sword, which is a reconfigured DenGasher.