I actually just completed it, I ran into all the problems people described about warden Hywell disappearing. On the third attempt, I tried something different. Before I released the four prisoners I went up and talked to the warden. He was there but told me to release others first. When I released the prisoners and went back up the ramp he had a star over his head. Not sure if that did anything but talking to him first seemed to fix whatever problem I had the previous two attempts. Also I interrupted the first attempt the priestess did at summoning so I only got 2 exploding adds, but she died before they could heal her.