I have a level 15 mage character, and I'm playing the quest "The Only Cure". I've made it into Bthardamz Arcanex, battled my way past Afflicted, Dwemer, etc., and now have reached Orchendor himself. The problem is, I gave him a dual-casted Fireball, a dual-casted Chain Lightning shot, and a dual-casted Frost Rune. My Destruction is at 57 or so, so these spells should pack a punch. None of them did any damage! Fus-Ro-Da didn't even seem to work. What do I do??

Is he using wards ? My mage used Ice Form shout, and then blast him with double casted lightening.

Summons that carry Weapons, Bound Weapons, He has an absurdely high resistance to Magic.

Or rise dead/summon Dremora Lords.