He is a rather warm hearted fellow isn't he?
Get all magic resist items on, and use the best healing potions that you have. I was able to get away with using the limited healing potions. Just run up and get the stuff in green smoke and run back. There is a skeleton right before the smoke, run around it.
Chant the spell in the hall and then when he's human, promptly beat his sorry as into the ground!
