I think I found a bug. In the inverted world, in Beamos Baracks. direct north on Level 2 area with the fans. Right after the fan section, there is a transition room with the two big ropes and 4 gold statues, where there is a gate blocking the door. I can't get the gate open and there are no monsters in the room. I have one reg key left and the boss key. Then I discovered there are some monster stuck in the wall (about 9, three different areas). They materialize one at a time. I kill one, exit, re-enter, kill another, exit, etc (kill total of 4 trapped monsters bottom wall, 4 trapped monsters left wall, 1 trapped monster top wall, if I remember correctly). I don't know if this is a bug and the room is suppose to be filled with monsters. And the monsters can't be reached by sword - I have to use bow & arrow.