I seem to be stuck in trying to kill this freaking lich... I can kill him and then he is unleashed into demigod form (when he's a floating skull) and I can't hit/hurt him at all and I can't figure out why I can't do anything to him... any help would be appreciated!!

ThreeD

Spoiler>>>>>>>>>>>>.
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1. Get yourself a +4 weapon (eg Staff of Rynn from Adventurers Mart) or Melfs Minute Meteor spell.
2. Buy a Protection from Magic scroll from the Adventurers mart and cast it on the person who will wield the +4 weapon. This will protect you from his imprisonment spells.

or

3. Buy a Protection from Undead scroll and cast on the same person. He will ignore that person and you can attack with impunity.

This might take quite a bit of hammering away at him but in the end you will be surprised at how easy it is.