When you get separated from the boy and end up with the Amazon (futa) and the Thief in separate cell's. The fight with Taramiel and her minotaurs should happen normally after being defeated she should leave the cell. Then you go see the boy in the other room where Irisviel is punishing the boy, then you fight the Succ, then get the curse book, then leave the Underdark with Amazon and Thief.