any good ideas on the final battle, i cant get the slayer below barely injured, he just goes back to uninjured...

are you still in elven city or in hell? killed all parasites? all demons) you need to breach/pierce his magics and use non-magical weapons and keep wailing on him

good luck

I hope you have collected many high level scrolls during the last chapters...since they can make the final battle much more easy.

I had Nalia casting time stop with a scroll to cast breach and some offensive spells, had Aerie casting time stop with a scroll to heal...used 2 sequencers of magic missiles...
And my three melee-ers finished him off.

Just don't attempt the battle unprepared, every wand, buff and items (ring of the ram comes to mind) can turn the odds towards you.