This is The Underkeep variant where you have to find and free the prisoners. In the last room, there were a bunch of mobs and two prisoners, each with a group around it.
the last 2 prisoners were not trapped by the ice block or poison totems like the others were.
i killed the pack around one of them and everything was fine. The other one is standing there at 34% health and not counting as the last prisoner needed. i can not go to the boss because the door is locked until you have 13 prisoners rescued.
I an soloing this 8 delve and everything was okay until this happened. Been in here a while now and have wasted assorted buffs and my playing time. GG
EDIT: I started clearing the rest of the room including bringing 3 of the mobs that do aoe on top of the last prisoner. after 2 the prisoner went to 100% health. the very last mob i pulled onto the prisoner did trigger the last part. i did not clear any of the previous rooms to free those prisoners, so idk if it was necessary here or somehow unbugged the npc.