Gerenth Ryback

A Deathlock of Apep and orchestrator of the attack on Amun'hn. Previously a shadar-kai until he became undead. Felt betrayed by the Raven Queen, so he defected to Apep who immediately turned him into a powerful deathlock. Angry, smart, cold, cunning.
He's the man in the black cloak that Hecatate saw during Quest: Trouble in Alo and the one who's been releasing monsters into different towns to hopefully try to weaken their defenses before the harvest festival attack.