Blood magic armor with fire resist so that he can't hurt you. Tart/paper/thaum rapier with nothing but Quartz upgrades does 7 damage per strike (I'm 99% sure of that, at work, can't check, but if needed, I'll check it tonight). Summon, and smash him into a wall over and over. Collect loot.
Tart as in... That max tier metallurgy 3 magic metal? It's got good damage, but if everything he is using and doing caps out at four damage... Including Fall Damage, by the way, it's very likely that your rapier will do 4 damage as well.
It's also very likely that he has a high magic defense and an all but impossible to beat armor value. "Smashing" him into a wall would be hard and a bit counter productive seeing as he can use Firestorm, which will hit you and since you are so close to him, heal him while ruining your armor. Unless it doesn't take damage from fire at all when it has that effect, which would be nice, but if it doesn't, you're gonna need a BIG soul net to keep that safe for long.
And honestly, the loot is a Red Infinity Orb and if it's a 100% chance, a hat that looks funny and grants you 100% immunity to fire damage. That's it. Unless you're doom driven to complete the "set", there isn't a hell of a high need to fight him at that point. That point, of course, being roughly magic level 90.
What is your current magic level? If it's above 90, then I'd say you may not have a badass enough offensive spell in hand to ruin him, with the much needed defense as well. Just stack what you know will hurt him most, and crank the damage up. Even an augmented Blizzard isn't as badass as a Augmented Blizzard with three AoE increases and 5 damage increases. But remember, Blizzard can only be cast once before it has to "cool down", as it were, as it can only sustain one active blizzard per player.
Use your full set of magic knowledge. Don't fight him alone, use a summon as well! Don't wait for him to heal, use a "contingency: fire" on HIM with the Random Teleport effect! Find a couple Nitro-Creepers and keep them close but far enough away that they can't explode on you, then cast a projectile charm spell on them once in a while to make one join your cause and blow up on him!
Find a way to get Light Mages in the Nether and set up a MFR Autospawner for them near the fight! With the Mage Posse talent they can be told to follow you at the cost of a summon slot, and with the Mage Posse II talent they will automatically use the silver tier effect Magic Link(or whatever it's called) that allows them to lend you mana when you are out of it.
For clarity sake, and as it bares repeating, again, @
Mahoka, what is your current magic level?
