Early in the game when I was at level 2 I got back to level 1 to find a shop to sell item. I pulled a random lever and saw a strangely positioned door. I opened it and there it was Lord Dredmor in a shop. I just shop a bolt of mass destruction, got a potion of invisibility and survive until he died. There the game end. I was only at level 2
This was mentioned before -- it's a known bug that only happens with pre-1.05 save games, and only on levels you've previously explored.
