I have been stuck trying to complete the final challenge for quite a while now. The first three were easy by comparison. No matter what I do the waves of spirits never ends, and I can not kill the fireballing mage unless I sneak in and pelt him with the ocasional arrow or range spell while dodeging his nasty fireballs, and in the attempt to do so I've spent hours hitting him for measly 3-5 arrow damage once in a while until I either get tired of the attempt or make a mistake and trigger the spirit waves. There has got to be a better way.
You don't need to kill him, just survive for a few minutes. Stand under him during the trial, as he moves to one of three ledges move with him. He can't hit you from there.
