My char:
lvl 16 Sorceror
staff og magi, robe of vecna, boots of speed,
Str. 19 (girdle of hill giant strenght)
Dex. 19 (Elf)
Con. 18
Int. 18
Wis. 18
Car. 18 (ring of human influence)
As you can see i had quite good abilities
The only 2 necessary spells: Mordenkainen Sword (lvl 7) and animate dead)
Before going to his chamber, go to the adventurers Mart, and buy two Protection From Magic from Ribald, and 5 scrolls of Melfs Meteors (Is that what they are called?).
Summon one skeleton Warrior next to where kangaxx spawns. Talk to him and wake him. Go to the corner where the stairs are, so that he cant see you. Let him cast his Time Stop, and use his magics on you're single skeleton. When the Time Stops stop, you're skeleton is dead. Now, create 3 skeleton warriors more, haste them, and send to attack kangaxx. These 3 will easily kill his first form, and when the "Near Death" appears, summon two mordenkainens Swords. Cast the PFM on them, and send them to attack his demi-lich form.
When this is done, let you're sorc carefully go and spot kangaxx. Be sure that he casts his imprisonment on you're Swords. The rest is very easy. Use the meteor scrolls, and attack him. By doing the whole thing right, he should be dead before you're swords unsommons.
Hope you could use this information, if not, i've just wasted my time