Go to the SoA forum and run a search on "kangaxx". One demi-lich is much like another.
Dundee's sig isnt used in all of his posts, but it is used. Might have to hunt a bit for it. Links in it are vey useful.
www.baldurdash.org has a section "50 ways to kill your kangaxx". A humerous look at methods of offing Kangaxx, and it applies to this one as well.
This demi-lich dosent have any scripting, so you can use a protection from magic scroll or a protection from undead scroll to render him harmless. Mace of Disruption will kill him extremely quickly. Otherwise +4 weapons should hurt him. Magic is virtualy useless against him.