[F. Gottwald]

well, buffing up beforehand could help... with your level, you can do just about anything he does, and you have tons of useful items that could give you an advantage... here a few things you might do:

turn into a mustard jelly and laugh at his puny attempts to hurt you (can´t remember if he summons a lot... if he does, change back briefly and cast a death fog or something like that)

use area spells against him (dispelling opponents spell protections is too much of a hassle... especially if you can just bypass them)

use hordes of summoned monsters to soak up the damage (or a few hakeashars)

use a scroll of magic protection (on yourself, although using it on him would be more amusing)

i´m not sure if all of these work well... can you give me a list of the spells he has up? then i could be slightly more specific.