Preyas

Preyas is a humanoid chameleon-like Bakugan, who is able to change his attribute. Initially Preyas has the Aquos attribute, but can change at any time to Darkus and Subterra or back to Aquos. He is Marucho Marukura's Guardian Bakugan in Bakugan Battle Brawlers and in Bakugan: New Vestroia from episode 26.

(Source: Bakugan Wiki)