I'm in hell and I can not waste him. Ive killed the demons, then I make him waste all his remainder spells on a sacrifice, usually Viconia and then I attack him. He fights back with his claws and kills us. I attack him and as soon as he gets to "Injured" status, he somehow miraculously goes back to "Uninjured" stats even though I don't see him using a spell and re-healing. Please help.

If I am not mistaken, Jon regenerates 3 hitpoints per second whenever you fight him in hell. What you should do is to have your mages cast anti magic protection spells on him (breach, spell strike, rubyray reversal ...etc) and also have you cleric with true sight on. Then pound away with remain characters, keep fighting as this is a looooooooooooooong fight.

When you hurt him enough, he will warp to another part of the map and make sure you chase after him ASAP due to his hitpoint regeneration. Try not to sacrifice characters as they can really help you surround him and pound away.

Good luck.

Try summoning monsters, elementals, undead to take the brunt of his spells for you instead of sacrificing one of your NPCs