Unalaq

Unalaq is the chief of the Northern and Southern Water Tribes and the primary antagonist of Book Two of The Legend of Korra. He is Korra's uncle and Tonraq's brother, a deeply spiritual man who seeks to reunite the physical and spirit worlds. Unalaq is a master waterbender and one of the few people capable of spiritbending — a technique that can calm or corrupt spirits. His true agenda involves freeing the dark spirit Vaatu during Harmonic Convergence to become the Dark Avatar, an entity that combines human bending with Vaatu's chaotic power. As the Dark Avatar, he nearly succeeds in plunging the world into eternal darkness.