Kangaxx the LichEdit
When Kangaxx first arises from his tomb, he is a fairly standard lich, albeit more powerful than a standard lich, or even the guardians of the parts of his body. He wears the powerful Ring of Gaxx, granting him rapid regeneration, bonuses to his Armor Class and saving throws, and adding to his innate magic resistance.
It is very important for the party that at least one person not be protected from undead, because once Kangaxx is down to 1 HP, he stops fighting and speaks to the party before revealing his true form.
Kangaxx the DemilichEdit
Once Kangaxx reveals his demilich form (which is essentially just a floating skull), the party is in for a difficult fight. Kangaxx the Demilich is 90% resistant to all physical damage and, like adamantite golems, he can't be hit by anything with less than a weapon of at least +4 enchantment. On top of that, his saving throws are all 2 steps better than his lich form, except save vs. spell, which is 3 steps worse.
Since Kangaxx is (effectively) still 'wearing' the Ring of Gaxx, he regenerates at a phenomenal rate.
Kangaxx is one of the toughest opponents in Baldur's Gate II: Shadows of Amn. His lich form is bad enough, given the regeneration from the ring, but his demi-lich form is even worse. The demi-lich is immune to all spells level 1 to 9 and on top of that immune weapons with enchantment less than +4. It can cast the spell Imprisonment unlimited number of times and can also use an area effect similar to Wail of the Banshee or Finger of Death.
There are a number of ways to prepare for the fight. The easiest way is to use a Scroll of Protection from Undead, which will make Kangaxx completely ignore the party. However, as stated before, at least one party member should not be protected in order to initiate the transformation of the lich to a demi-lich once the lich's HP drop to 1.
Another, less useful protection spell is Scroll of Protection from Magic, which will protect party member from Kangaxx's spells. Mage spells like Spell Immunity to abjuration will protect the caster from imprisonment, but will leave them vulnerable to death spell effects are thus the least useful option.
Only a limited number of weapons can hurt the demi-lich, as stated above, of +4 or better enchantments. The Staff of Rynn is the most easily obtainable one, being sold by Ribald Barterman at the very beginning. Carsomyr, Cutthroat, Dragon's Breath (weapon), The Wave, Crom Faeyr and similar work just fine as well, though most of them become available late in the game. There are also some exceptions that can hurt Kangaxx without being explicitly named as +4 weapons, namely the improved Mace of Disruption and Daystar. The Burning Earth and Azuredge have been proven to function as well, despite not meeting the criteria, at least in an unmodded Shadows of Amn. Any missile weapon can also hurt Kangaxx, given that their projectiles (bolts, arrows, darts, bullets) are at least +4. The Cloak of the Stars produces thrown weapons that deal damage to Kangaxx.
The spells that function against Kangaxx include:
Search Athkatla for the hidden pieces of Kangaxx's body so the lich can finally be destroyed.