Not sure why you are having difficulties with Kangaxx as you are outfitted to defeat him.
But a few questions: are you facing his first or second form? What level are you? Are you using protection from undead scroll and if you are did you use it at the correct moment otherwise there is a bug? Did you get the dialogue when he went into his demi-lich form? Are you positive that you have +5 weapons?
If you get Kangaxx in his demi-lich form just using protection from undead scrolls (after the dialogue) and with +5 weapons makes it possible to defeat him quite easily (its almost cheating using the scrolls). Don't use spells as his demi-lich form is immune to them - just hit away with +5 weapons and eventually he should go down - his demi-lich form doesn't have a ton of hp.
But as others have said - make sure your game is patched correctly because who knows what bugs earlier patches have - use the latest patch.
For what it's worth, right now, Daystar is striking as a +2 weapon. In 1.3 it was striking as a +4 weapon. It can be restored to that with Near Infinity, and I think that's more in line with what the developers wanted. Heck, IMHO it would be nice if it had a +4 THACO, too, with the proviso that you can no longer use cheese to get it (make the guardian a little smarter).
As for Kangax, I must confess to using cheese to beat him. Until I read some of the more sophisticated tactics on this board a couple years ago, I didn't think it was possible to beat him any other way. In fact, I was proud that I at least figured out a cheesy solution on my own.
An easy, if incredibly busted way to take care of him involves Yoshimo, Korgan and Keldorn.
Have Yoshi set up a bunch of traps where Form 1 will spawn in at. This'll probably kill it, or at least make it easy for you to finish it off.
Once he turns into a Demi-Lich, stand Korgan right next to him and have him use Rage - This makes him immune to Imprison, which Kangaxx will spam on the closest character (Korgan, in this case) to no avail.
Now for the last part, you need Keldorn, and you need him to have Carsomyr - its range means that Keldorn won't be focused on by Kangaxx, and because it's a +5 weapon, it'll be able to take him down fairly quickly.
This is more or less how I did it, except I had my Charname as a Berserker instead of using Korgan.
You can do that even earlier using the staff +4 that you can buy in the very early game, the sling +5 with unlimited ammunition can help to kill a little faster. The vanilla 2nd form is quite easy as he uses only 1 type of attack in a predictable way, very dangerous, but if you know how to make one of your chars immune not much challenge is left. He is almost impossible if you don't have the knowledge, when you have it is too easy. The sad truth is that Korgan has a big chance to go there solo with that staff in the early game, enrage and win... No Thief and Pally needed. I prefer Tactics Mod Kangy, the use of traps is prevented or made very difficult and he targets all the members of the party using that spell and also the other high level spells a powerful Demilich is supposed to have. You can not rely on easy tactics, you have to wait until the party reach an appropriate level and use a sound tactic. I don't suggest that modded battle for new players, is too difficult, I want just to point how attention was used in avoiding easy exploits like traps on a spawn point (even if here Charname has very good clues about what will happen...) or shield the whole party using a single protected member. Is a sad joke to see how one of the hardest battles of SoA is so easy when you know the tricks.
Another important thing to note is that some innate spells like e.g. Inquisitor's Dispel Magic are in fact "lvl 0" spells - which means they do not fall under spell level immunities AT ALL and will always work against Liches/Demiliches (level-based rolls still apply, of course).
Dispel magic works strangely on all account, even the mage/priest spell works on any enemy (provided you succeed rolls) except those immune to abjuration.
Interesting to note, for these spell immunity discussions: For whatever reason, demi-liches in the unmodded game aren't immune to the blind effect of the lvl 7 spells Nature's Beauty. You can simply have Jaheira or your own druid or ranger/cleric cast it (protected by shield of the archons for safety against imprisonment), blind the bugger, and then sit back and kill him with stuff like MMMs, Energy Blades, the Sling of Everaard's +5 bullets, even melee weapons with 2 range (generally 2h weapons) that can hit like the Staff of Rynn +4, as blinded enemies can only see out to range 1.
This fight is still driving me insane. I can protect my party fine. 1st form dies instantly from Sunray. I don't seem to be able to do anything to the Demi-lich form. Hitting him with sling +5 and bullets +4, Gesen bow and whatever magic arrows it throws, and Staff +4. What little damage I can do get regenerated almost instantly.
Ring of the Ram does damage, but then it punts him away from the character I have set up to dodge imprisonment.
First form gave me no trouble at all, second form I gave Immy a girdle of giant strength, the best longsword in the party, (which was +5 from a mod) had her caste Haste, and Spell Immunity. Took a bit, but she got the job done before the duration ran out. The first form is pretty easily beatable by the Planetar HLA summons, too.
I've never had an issue with him. When in demilich form I have all my characters cast a protection from magic scroll on themselves and he can't touch them. Works like a charm. Note that you can't cast magic with that on so have your mage cast their shield disable spells first on the first form, when that dies then cast the protection.
Quite a few of the temples and 2 of the Scroll Merchants in Waukeen's Promenade sell Protection from Undead scrolls, what i normally do is make sure i have unlocked, or have a thief who can unlock, the chests and doors related to the City Gates Lich, the 2 Elemental Liches and obviously Kang. Once i do enough of the Unseeing Eye upper area to be able to fight the Elemental Lich there then i use the scroll, then a potion of Haste, Blap the 2 Elemental Liches, the Bridge Lich and Kangaxx using daystar, as long as it's a fighter type it's super easy and can basically be done right out of Chateau Irenicus. A Rogue can also do it but Kangaxx has a half decent AC so it takes longer.
With a fighter i usually have enough duration left on the scroll (chug a 2nd oil of speed when 1st runs out) to also do all the undead in the Graveyard, plus head into the Southern Tunnels where Korgan/Edwins quests are and kill all the undead down there too. I mostly play solo so kinda makes it easier as i don't need to use potions for multiple characters. All told it's about 150-160k Exp for 1 scroll duration
Yeah the prot undead scroll is cheese, but lets be honest it's a cheese encounter. You need +4 weapons to damage him, he chain casts imprisonment (no save or magic resistance) and Wail of the Banshee (AoE save or Die), and that assumes you can get past his 1st form with enough spells and protections in place not to get blapped.
To be immune you need either a scroll (magic or undead), Spell immunity Abjuration (self cast only) Berserker rage (Barbarian doesn't cover imprisonment), unsure if spell trap will work, it may, but it'll use 9 out of 30 spell levels if it does so you get at best 3 castings. Then you need Death Ward or something that makes you immune to Death Magic, or extremely good saves and/or magic resist, or Spell Immunity Necromancy (again self cast).
A Mage can't really do it on his own, can make themselves immune for sure, but it's not like you are going to take the skull down with 1 APR before stuff starts running out.
A priest can't do much against Imprisonment, Shield of the Archons maybe will work for a few, not tested but again 1 APR, Sunrays you really need at least 2 able to cast it or use items.
At this point you are likely looking at Minsc and/or Korgan just rushing it and rage-dumping with Undead slaying weapons and TBH i fail to really see the difference between using a scroll to become immune or using a class specific ability, the end result is the same you just don't need to specifically use 2 NPC's or be a Berserker Bhaalspawn.
For the record i have actually killed him as a solo level 12 Thief w/o using a scroll before, but took a few reloads and some extremely specific preparation and items. Daystar for the 1st form, stacked traps in the Top right of the room, with an extremely carefully aimed Ring of the Ram to push the skull into the traps.
I would definitely advise a non-cheese kill at least once, but there's something like 11 Protection from Undead scrolls in the game in total, lets be honest if you don't use one on Kangaxx and/or the Demilich in Watchers Keep then you will Probably end up using some other form of cheese such as casted spell immunities/Rage. I like a challenge, but the list of ways to negate Imprisonment AND wail of the banshee is pretty short and since that is all he can do for attacks...grab a glass a Red to go with a fine aged Brie
Comments
But a few questions: are you facing his first or second form? What level are you? Are you using protection from undead scroll and if you are did you use it at the correct moment otherwise there is a bug? Did you get the dialogue when he went into his demi-lich form? Are you positive that you have +5 weapons?
If you get Kangaxx in his demi-lich form just using protection from undead scrolls (after the dialogue) and with +5 weapons makes it possible to defeat him quite easily (its almost cheating using the scrolls). Don't use spells as his demi-lich form is immune to them - just hit away with +5 weapons and eventually he should go down - his demi-lich form doesn't have a ton of hp.
But as others have said - make sure your game is patched correctly because who knows what bugs earlier patches have - use the latest patch.
For what it's worth, right now, Daystar is striking as a +2 weapon. In 1.3 it was striking as a +4 weapon. It can be restored to that with Near Infinity, and I think that's more in line with what the developers wanted. Heck, IMHO it would be nice if it had a +4 THACO, too, with the proviso that you can no longer use cheese to get it (make the guardian a little smarter).
As for Kangax, I must confess to using cheese to beat him. Until I read some of the more sophisticated tactics on this board a couple years ago, I didn't think it was possible to beat him any other way. In fact, I was proud that I at least figured out a cheesy solution on my own.
Have Yoshi set up a bunch of traps where Form 1 will spawn in at. This'll probably kill it, or at least make it easy for you to finish it off.
Once he turns into a Demi-Lich, stand Korgan right next to him and have him use Rage - This makes him immune to Imprison, which Kangaxx will spam on the closest character (Korgan, in this case) to no avail.
Now for the last part, you need Keldorn, and you need him to have Carsomyr - its range means that Keldorn won't be focused on by Kangaxx, and because it's a +5 weapon, it'll be able to take him down fairly quickly.
This is more or less how I did it, except I had my Charname as a Berserker instead of using Korgan.
The vanilla 2nd form is quite easy as he uses only 1 type of attack in a predictable way, very dangerous, but if you know how to make one of your chars immune not much challenge is left.
He is almost impossible if you don't have the knowledge, when you have it is too easy. The sad truth is that Korgan has a big chance to go there solo with that staff in the early game, enrage and win... No Thief and Pally needed.
I prefer Tactics Mod Kangy, the use of traps is prevented or made very difficult and he targets all the members of the party using that spell and also the other high level spells a powerful Demilich is supposed to have. You can not rely on easy tactics, you have to wait until the party reach an appropriate level and use a sound tactic.
I don't suggest that modded battle for new players, is too difficult, I want just to point how attention was used in avoiding easy exploits like traps on a spawn point (even if here Charname has very good clues about what will happen...) or shield the whole party using a single protected member. Is a sad joke to see how one of the hardest battles of SoA is so easy when you know the tricks.
Well, he's got petrified and died.
Ring of the Ram does damage, but then it punts him away from the character I have set up to dodge imprisonment.
This fool just refuses to die!
With a fighter i usually have enough duration left on the scroll (chug a 2nd oil of speed when 1st runs out) to also do all the undead in the Graveyard, plus head into the Southern Tunnels where Korgan/Edwins quests are and kill all the undead down there too. I mostly play solo so kinda makes it easier as i don't need to use potions for multiple characters. All told it's about 150-160k Exp for 1 scroll duration
4 sunrays is enough - 2 for his first form, 2 for his second.
You can get one sunray from Daystar and another from the Helm of Brilliance, plus whatever your clerics can cast.
To be immune you need either a scroll (magic or undead), Spell immunity Abjuration (self cast only) Berserker rage (Barbarian doesn't cover imprisonment), unsure if spell trap will work, it may, but it'll use 9 out of 30 spell levels if it does so you get at best 3 castings. Then you need Death Ward or something that makes you immune to Death Magic, or extremely good saves and/or magic resist, or Spell Immunity Necromancy (again self cast).
A Mage can't really do it on his own, can make themselves immune for sure, but it's not like you are going to take the skull down with 1 APR before stuff starts running out.
A priest can't do much against Imprisonment, Shield of the Archons maybe will work for a few, not tested but again 1 APR, Sunrays you really need at least 2 able to cast it or use items.
At this point you are likely looking at Minsc and/or Korgan just rushing it and rage-dumping with Undead slaying weapons and TBH i fail to really see the difference between using a scroll to become immune or using a class specific ability, the end result is the same you just don't need to specifically use 2 NPC's or be a Berserker Bhaalspawn.
For the record i have actually killed him as a solo level 12 Thief w/o using a scroll before, but took a few reloads and some extremely specific preparation and items. Daystar for the 1st form, stacked traps in the Top right of the room, with an extremely carefully aimed Ring of the Ram to push the skull into the traps.
I would definitely advise a non-cheese kill at least once, but there's something like 11 Protection from Undead scrolls in the game in total, lets be honest if you don't use one on Kangaxx and/or the Demilich in Watchers Keep then you will Probably end up using some other form of cheese such as casted spell immunities/Rage. I like a challenge, but the list of ways to negate Imprisonment AND wail of the banshee is pretty short and since that is all he can do for attacks...grab a glass a Red to go with a fine aged Brie