Zolin, blood priest revived.

This happened after i killed the duo and finished the quest. I was on the other side of the map from the boss room picking up loot when Zolin popped up and attacked me then disappeared. I went back to the boss room and they were then and it had 0hp and was immortal.

Same behavior when I portaled to town after killing the duo in order to sell loot.
After I returned he revived with 0 HP and stopped me from talking to the hooded one in order to finish the quest.

I had the same problem. We have to return to Kingsmarch (Act 4) to talk to the NPCs to complete the quest.