Frog - How does a Mage take down Great Unclean One in Arena?

[GrimaTheBold]

CL 44 Mage of Armageddon/Sorcery. I just took out Mummy King and Nightwalker in Arena pretty easily, but Great Unclean One is next and I don't see how it's theoretically possible for a mage to do 6600 damage in Arena.

Lets assume I go with Breathe Plasma. Cost is 25, and I have 375 SP, so that's 15 times I can cast it. My current damage is 254. So that's 3,810 points of damage, leaving me 2800 HP short of killing him. Obviously if I gain a few more levels and find some better gear (like a better Wizardry ring, currently wearing +12 damage) maybe I can close that gap but I still don't see how I get to 6600 HP.

Is there some way of restoring mana that works in Arena that I'm not seeing? I mean there's always Eat Magic, but munching on wands to regain SP while Unclean is quickly killing me seems untenable.

Is the secret something that requires waiting for the 4th Armageddon Spellbook? Does the math work out with Breathe Mana or Shards? And do you have to wait for 4th Sorcery book for GOI? Even then I'm having a hard time picturing it working.