End mob, click the two pillars on top of temple to spawn him. He changes his defenses periodicaly. Look at his first beneficial effects, the first one that looks like a ghost.
Activated by the two stone settings on each side of him (red writing on the floor), floor opens and he rises up; AoE noxious damage, curable; Resolve check, nox may one shot low Resolve players, duo this until you can tank him, or clear the ghosts and kite him.
this mob casts fear (arms wide motion while casting), interruptable; there are 4 wraiths up on ledges like this, one of them carries the first stone setting to spawn Meld of Vapor