After I'd cracked the Training Hall, I used to go back in the front door and immediately hit return as soon as the position loaded. I could then move to the end of the line of lizard orcs that were practising drill, and cast 3 Poison Clouds. The clouds would move right down the line, hitting one orc after another. It used to kill one or two, and leave the rest so badly hurt that it was very easy to kill them in melée in the next couple of rounds. Very good for experience, and a new artifact every time in the black chest.