Negataros appeared in 2008 movie called Kamen Rider Den-O & Kiva: Climax Deka. Negataros is the Kamen Rider Nega Den-O (仮面ライダーネガ電王 Kamen Raidā Nega Den'ō, lit. "Nega Power King") and is the fictional villain of the Japanese 2008 Kamen Rider Series movie, Kamen Rider Den-O & Kiva: Climax Deka.
Following the events of Kamen Rider Den-O, Negataros (ネガタロス Negatarosu) and a select few Imagin are stray Imagin who evaded the fate of the other evil Imagin when Kai ceased to exist in the final episode. Soon afterward, he steals an extra Rider Pass before arriving to restore the future where the Imagin exist by recruiting mobsters and members of the Fangire Race to his aid. In Climax Deka, Negataros had to deal with both the DenLiner Police (デンライナー署 Denrainā Sho) led by Ryotaro Nogami, an inside man in the form of Yuto Sakurai, further worsened by the brief meddling of Wataru Kurenai.
In the end, Negataros' plan is foiled and his armor is destroyed by the Double Boistous Kick & Darkness Moon Break of Den-O Climax Form & Kiva before he finally meets his end in battle against the Den-Liner, the Zero-Liner and Castle Doran.
Negataros is also featured prominently in the S.I.C. Hero Saga (S.I.C.ヒーローサーガ Esu Ai Shī Hīrō Sāga) in Hyper Hobby Magazine. The story is a retelling of the events of Climax Deka featuring Negataros traveling to April 3, 1971, to team up with the Shocker organization and combating Den-O and the Tarōs along the way.
A cocky and arrogant Imagin, Negataros shares a few similarities with Momotaros aside from looks and appearances. They are both quite confident of themselves and are quite eager for a fight. Unlike Momotaros though, Negataros is an evil Imagin who showed no desire to protect the timeline or innocent people but instead to destroy the current timeline while willing to murder countless of innocent people to do so.
Even though Negataros can only transform into one form which closely resembles Den-O`s Sword Form, his powers seemingly exceed all of Den-O's basic Form and possibly even Climax Form as well. This is hinted when he managed to survive being struck by a double Rider Kick from Kiva in Kivat Form and Den-O in Climax Form and instead of being defeated, only lost his Rider Form without (seemingly) being seriously injured.
Even when confronted by the DenLiner, ZeroLiner and Castle Doran, Negataros managed to somewhat hold his own with the Nega DenLiner until he was ultimately defeated proving how skilled he is at using it.