"Savage"

Savage was once a Toa (possibly of Earth, given his black coloring) who was infected with Visorak venom and became a Toa Hordika. When this happened, his teammates didn't recognize him and attacked him as a monster; this caused his feral side to take over until he could only make grunts and growls, and he lost control and injured his friends. The Dark Hunters found him, and The Shadowed One convinced him that his team allowed him to become a monster. Besides being a skilled hunter, Savage's Rhotuka spinner can paralyze enemies, and his tri-claw can liquefy solids. He is occasionally overtaken by madness and has to be locked up for everyone's protection.