Kamen Rider Kuuga (Rider)

In all versions, Kamen Rider Kuuga (known simply as Kuuga, in the original series) is a fighter who fought the Gurongi assuming his form through the Arcle created for the Linto Tribe. However the "Kuuga" character was not invented by the Linto but is actually borrowed from an incomplete Gurongi character, tied to N-Daguva-Zeba (N-Gamio-Zeda in Kamen Rider Decade) who like Kuuga possesses an Amadam.

Kuuga's Forms
Kuuga is the Kamen Rider with third most forms to date (when adding both the forms assumed by Godai and Onondera), 14 in total, one shy from Kamen Rider Double with 15 different forms, and 115 shy from Kamen Rider OOO with 129 different forms (if you exclude the Random Combos involving Medals from the Movies or anywhere outside the series). Aside from his first form, Growing Form, he had four base forms that he relied on and would upgrade throughout the series, and in Decade, even Ultimate Form also gained an upgrade which he can alternate in between, occasionally prefaced by saying "Cho Henshin!" (超変身!, Super Transformation). His armor and eyes would change color depending on the form. Like the Gurongi of the Go Group, Kuuga can alter any item he has into a weapon by temporary changing its atomic structure after unlocking his other forms.

Rider Cards
Several Rider Cards allow Tsukasa Kadoya/Kamen Rider Decade to access the power of Kuuga.
 * KamenRide Card: Regained when Tsukasa gains Yuusuke's trust. Decade uses the card to assume Kuuga's Mighty Form.