I just happened to read some old posts describing all kinds of cheesy ways to win this fight. A perfectly "legal" way to kill this critter is with a single Dragon's Breath (just one ping, Vasiliy).
Admittedly, you must have a high-level Mage/Sorceror in your party (there are no scrolls or potions of this spell).
I'm trying to win this fight right now but my Mage isn't far enough along and it's not looking good.
(update) I just pickpocketed the Ring of Gaxx. I used a Protect From Undead scroll and jacked up my pickpocket skill and VOILA! It's not as satisfying as frying the skull but I can come back later and do that. In the meantime, I've got use of the ring.
I didn't know about dragon's breath... I think I'll use this tactic next time.
Another way to beat Kangaxx without cheese is putting either Minsc's or Korgan's rage ability to good use. Give them a powerful enough weapon (mace of disruption comes to mind) and activite the rage ability so they won't be vulnerbale to Kangaxx's imprisonment spells.
She says: Lou, it's the Beginning of a Great Adventure
A demi-lich like kangaxx is immune to all 9th level spells and lower.
Theoreticly Dragon's breath is of the 10th or quest level spells but it occupies a 9th level spell slot.
Someone needs to verify if Dragon's Breath really works.
But then again...waiting until you get dragon's breath is not that good of an idea because you really should have more than sufficient equipment to deal with Kangaxx the melee way by then
Geez, Tolwyn, are you the BG2 police? I've used Dragon's Breath several times on both Kangaxx and the other demi-lich in Watcher's Keep; trust me ... it works.
I recall beating Kangaxx in his Demi-Lich form with Keldorn equipped with Carsomyr and Ring of Ram, Korgan gone enraged, Nalia throwing Melf's Minute Meteors, Minsc using Daystar and Anomen casting False Dawn. Hard fight but we prevailed!
• "You cannot pass."..."I am a servant of the Secret Fire, Wielder of the Flame of Anor, You cannot pass. The dark fire will not avail you, Flame of Udun. Go Back to the Shadow! You cannot pass."
Gandalf the Grey