I thought this would be a nice place to talk about this half naked boss of destruction. I'd post what strategy I used to kill her but I haven't played the game in a while and can not remember ;)

<font face="Verdana" size="3" color="#00FF00"> If you play with Project Auril you get to meet her older sister in the Gloomfrost.

Anyway I usually send one person usually a thief to start the conversation. Bring the thief back. Cast spells like entangle, and web at the door than area effect spells like spike stones and such on top of that. Send fighters and summons to deal with the Yaun-Ti priest that come from behind. By now the army is getting stuck and taking damage so just finish those off with some mass effect storm spells like "ice storm" or "acid storm". Than send hasted fighters and summons at Yxonumai. Priest and mages are used as support casting buff spells. Injured characters retreat to heal, send them in again. If using a bard have him sing. Pretty easy but interesting battle. Similar solo, but I just use the smaller adjoining room to retreat, and summons are most important. </font>

The Group: Ranger, 2 fighters, fighter/thief, Druid, MU/Cleric.
The plan: Clear the top rooms above Yux's room. Send in your fastest person to activate the talking sequence. High tail all your people to the top chamber and goto the back room. Put your 3 fighter types at the door so know one can get to you Mu or druid. Have your Cleric cast bless and recitation. Have your druid cast spike stone and that thorn spell. This will take care of Yux's minions. You don't have to worry about them casting spell they get hit too often. Yux will make it through that mess and then have your fighters take her down. This is an easy fight if you can take the minions out of the picture. Make sure you have at least +2 weapons on your fighters.

I actually found it easier to beat her with a solo Cleric/Ranger equipped with The Love of Black Bess and a sling than with a party.

I sent 2 fighters and my thief, with malee weapons striaght in to attack, her up close. They were blessed and hastened. My mage and 2 druids sent in commons, and they attacked all the fools on side with every spell they new. To my surprized my Mage used fire spells on the sneakie snake priest from behind and to them out. Once I took her down, I ran all the way out to rest. I may have lost some treasure, but I saved everyone, and I was all beat to hell

I'm with Ashsays on this one. One of my favourite tactics in BG/IWD is to fight in narrow doorways, especially when out-numbered. I usually retreat to the upper room and fight on my terms, I found this to be best in HOF and when soloing. I was expecting a really hard fight for my solo F/M but luck was on my side. I stood in the doorway to fight and the front rank of the attackers was two summoned skeletons - who couldn't damage me. So I left them alone while I killed off the dangerous enemies behind them with ranged attack. Nice one, solo character takes no damage, bad guys are wiped out.