A well trained character can also clear the temple without any tricks, as long as you have death ray resistance. The last time I was down there, I killed the archmage using nothing but thrown rocks. The other two times, I did it with a poweful but not slaying melee attack. One of them was done in the dark. The melee approach does have its price, but it's certainly a worthwhile option. Of course, a human priest is not the ideal character for that approach.
My hurthling barbarian killed him in melee with Vanquisher, I think, and his stats suffered greatly... Just don't do him in melee unless it's for coolness reasons or you don't have a choice.
ADOM Guides - whatever you wanted to know about playing a certain class, but have been afraid to ask!
Check out my youtube channel to see my ADOM videos, including a completed playthrough of the game. I try to give instructions, so if you want to see some place you haven't been before and get some hints on how to deal with it, this might help! There's also some other games featured there that you might find interesting.