[daan]

Ok ...
There are 2 ways of using a protection from Magic scroll ... one of them is casting it on your enemy, since Magic is resisted inside the sphere as well. All spells will fail, when you're surrounded by a Protection from Magic globe. The reason that the globe's gone, once you kill his Lich-form, is probably because he becomes something else, so the game doenst carry the PfM-globe over to the demi-lich form.

The Lich form can be hurt by sunray . .the Demi-lich form cannot .. I tried Fals Dawn, i tried Sunray . .both were ineffective.
Which in a way makes sense, because IIRC demi-liches are immuned to all but lvl 10 spells
( Melph's Minute M's excluded, since these are meteors, not spells)
The MoD CAN indeed hit kangaxx ... im not sure if its just the upgraded version, but the upgraded version usually kills him in one to two blows . .there are numerous posts describing that too ...
Its enchantment lvl ( NOT the THAC0-bonus) is +5 after the upgrade )

You can kill kangaxx both forms quite easily low-lvl using this method ... you only need a decent fighter OR a decent mage ....

Fighter:
Do the trademeet quest and receive the Flame's tongue (longsword) ... it's enchanted +4 against undead and WILL hit kangaxx in demi-lich form.
Now but both a PfM-scroll and a PfU-scroll. Cast the PfM-scroll on yourself and fight kangaxx in his original form , he'll be easy, as he cat hurt you with magic.
Once he transforms .. and only AFTER he transforms into a demi-lich,
cast PfU-scroll on yourself and whack him .. hell fall easy and fast.

Mage:
Same tactic for the PfM and PfU -scrolls .. but now memorize a lot of MMM's ( lvl 3 ) ... He'll fall quite easily that way.

As a mage its very possible to solo him without the help of scrolls .. by casting -Spell immunity: Abjuration-, this will negate the imprisonment spell the Demi-lich casts .. ( actually its a spell called "trap the soul" , but it works the same as imprisonment)
Now casting MMM's and Improved Haste will finish him off .. improved haste is very important, since the Demi-lich regenerates and flees sometimes.

For all other Liches, Daystar works great for a fighter