I have just realized that it is possible to beat Kangaxx without using any scrolls or spell protections, at low levels, just by using a weird trick with Jan's Flasher Master Bruiser Mates, the peculiar little skulls that people barely ever use, because of their pitiful damage and low enchantment level. I refer specifically to Kangaxx's demilich form, but the flashers should be just as capable of defeating his lich form.
First, some statistics. The flashers do 1d2+1 damage. They have a stun on hit effect that lasts for 12 seconds, with a save at -1 to avoid the stun. The stun effect does not bypass magic resistance, but has a spell level of zero, meaning it bypasses all spell level immunities. Kangaxx is immune to spell levels 1 to 9, but is not immune to stun. But the flashers have an enchantment level of 1, and Kangaxx can only by harmed by weapons with an enchantment of +4 or more. Jan has 1 base APR, or 2 if he uses the Light Crossbow of Speed. Under normal circumstances, Jan cannot even hit Kangaxx in his demilich form with his flashers.
However, there are two tricks that together allow Jan to hit Kangaxx with his flashers and stunlock him with a high chance of success. I have tested this and it works as intended, though I have yet to beat him with it. But if we have the right setup, it should be possible to defeat Kangaxx using an approach based on flashers.
The recipe is thus:
-Jan and a bunch of flashers (one stack of 20 should be sufficient)
-Firetooth +4 (the crossbow, not the dagger)
-One casting of Improved Haste
-One casting of Polymorph Self
-One casting of Shocking Grasp
-The War Hammer +1, +4 vs Giantkin, and somebody to use it (no pips required)
-The Flame Tongue, and somebody to use it (no pips required)
-And, of course, a way to beat Kangaxx's lich form, if the flasher method does not work.
All this can be easily obtained right out of the first dungeon.
Jan casts Polymorph Self, shapeshifts into a spider, and casts Shocking Grasp via a sequencer or a scroll. He makes on attack, expending the Shocking Grasp attack and allowing him to use normal weapons. He equips Firetooth and his flashers. We cast Improved Haste on him. He now has 8 APR with the flashers. Firetooth is there for the THAC0 bonus, but any other crossbow would work fine as well.
We have one person with bad AC stand next to Kangaxx. Going unarmored or wearing Missile Attraction +2 will work fine.
When Kangaxx comes out in his demilich form, he will spend his first round using the Demilich Wail, which we can survive without spell protections if we make our save. After that, he will start casting Imprisonment, and the only way to avoid it is to use spell protections or a scroll of Protection from Magic or Protection from Undead. In order to survive after the first round, we must kill or disable Kangaxx within about six seconds.
Normally, we can't hit Kangaxx with the flashers. But if we target our high-AC character with the flashers, the flashers will land a hit, explode, and affect Kangaxx as an area effect. Note that the flashers use a unique projectile that, unlike a normal Skull Trap, will not affect the party. We are basically attacking our own party so Kangaxx will be hit indirectly, while our own party will be safe from the flashers.
Kangaxx has a save vs. spell of 4. With the flashers' save penalty of -1, he should have a 75% or 80% chance of avoiding it. Jan will hit our target character 8 times in that first round unless he rolls a critical miss, which means Kangaxx's chance of getting stunned is equal to 1-0.75^8 or 1-0.80^8, which is about an 80% to 90% chance of stunning him. If we fail to stun him, he imprisons us. If we succeed, we can then try to keep him in stun lock by continuing to fire flashers after him, while the rest of the party attacks with the War Hammer +1, +4 vs. Giantkin and the Flame Tongue, or other +4 or +5 weapons if we have them. We hit automatically, so even at 1 base APR, we could take him down within 5 rounds. Kangaxx's chances of escaping stunlock within that time are very low.
Testing found that Kangaxx could in fact be stunned by the flashers, though he only took 1 or 2 damage from the hits, as Firetooth's fire damage bonus has a spell level of 6, which Kangaxx is immune to. I have not used this trick to beat him yet, but he can be stunned with flashers if we attack indirectly.
This means Kangaxx can be beaten at low levels without the defenses we would normally require. Jan and his flashers have tremendous potential if we turn him into a spider, and there's actually a good reason to wear Missile Attraction +2.