Zao'Kapazao, Vilebat Keeper, is a Unique Morlu Caster found in the Blessed Chancel in Act IV of Diablo III, added in Patch 2.2.0. He may be nominated a bounty target, and spawns for the Hellbreeder Nest event.
In combat, he gains Desecrator, Mortar and Jailer affixes. Up to 4 times, usually after losing at least 25% of maximum Life, he will teleport to one of the four corners of the platform, become briefly invulnerable (visually, shielded by a green force field) and summon 3 Vilebat Breeders, which, in turn, spawn hordes of Vilebats. Killing Zao'Kapazao ends the event (but does not kill the remaining monsters).