Recently I just killed Yxunomei on insane difficult with a party of 5. It was really hard since the bitch has magic resistance against almost every single spell and on insane she hits my party members like crazy. In one hit she damages around 50, so 2 hits almost kills anyone in my party.

So I thought we could have a topic where we can share good strategies against the main bosses.

Here is my first one:


Yxunomei:
Have your +2 arrows equipped at your ranged attackers (the one s with bows). The demon can only be harmed with +2 or better weapons.
Move all the party member but one to the room which is marked X on the attached map. The remaining member should have ring of freedom equipped or must drink a potion which has the same effect. Move this party member in front of Yxunomei's door.
Now, cast a Web or 2 and an Entangle or 2 on the spot marked O. Also a Grease could help. You can summon a few animals/skeletons just in case anyone got through your defenses. Well the demon will get through since nothing has an effect on her due to the magic resistance.
Then start talking with Yxunomei then run back to the party (you will not get stuck in the Web & Entangle due to the ring/potion). Right when you got back, start casting Spike Growth 3 times in a row on the same O spot. You can use also Spike Stones if you already have. Meanwhile start casting defensive spells with your Cleric like Prayer, Bless, Defensive Harmony on your party. As soon as the first enemy shows up, cast Haste on your party, then start pumping the +2 arrows into Yxunomei. She will be dead in 1 or 2 turns and everyone else will be taken care of the Spike Growth, but you can speed up the process with arrows and bullets.

It was the only strategy which worked against this demon in Insane difficulty, since she killed anyone in a turn as soon as she got near someone although my fighters had 80-90 HP that time.
An other note:
I don't have pure fighters, only fighter/thief, fighter/druid, cleric/ranger and fighter/mage. I may be able to defeat her with melee weapons if I had pure fighter since they'd have much higher hp.

I killed Yxunomei fairly easily with a solo dual-classed fighter/mage. Can't remember what level I was, but it was probably somewhere close to 6/15 or so. I had 18/91 strength and 18 dexterity, so I was getting good Thaco and damage buffs. I had found enough non-armor magic items to get my AC to -10. I was also a Master proficiency with bows and had equipped the magic bow (found in the room with all the Elite archer snake-guys to the south on this same level) that gave me 1 extra attack/round, so I could fire 3 arrows each round.

Before you walk into the room, buff your character with Mirror Image, Shield, Haste, Protection from Evil, Improved Invisibility and drink a potion of Giant Strength (the one that raises your strength by 5 points) as well as the Potion of Mind Focusing (the one that raises your Int and Dex by 3 points). For me this lowered my effective AC to -15 and I was getting something like +12 bonus to Thaco using my magic bow and + 7 to damage.

Then immediately walk in and talk to Yxunomei, taking the quickest response to provoke her into attacking so you don't loose spell duration time (I don't know if the game pauses during conversations or not, but just in case don't waste time talking).

Then immediately run back out of the room all the way to the door at the far end of the hallway, ignoring the 3 newly appeared snake-guys. The Door is locked, but no problems, we just want to draw out our enemy and make them come to us. Quickly cast a Web spell in the middle of the hallway. Very soon Yxunomei will show up with her goons in tow, and stand right in the middle of your web. Most of the goons will get stuck. She then casts Cloudkill on herself and this will kill all the surrounding goons who are stuck in the web.

Once she has cast cloudkill, start firing +2 arrows. She'll try and cast a few more spells, but as long as you disrupt them with your arrow fire, all you need to do is keep shooting at Yxunomei till she dies. Any straggler snake henchmen that happen to still be alive are not going to be able to hit you easily with your low AC. Finish them off once Yxonumei is dead.

You win.

Wow, thank you, yours is a really great strategy!

Big hell on insanity (almost made me left the game), however, she can be terrified by the horror Spell (Funny seem a true demon lord terrified). If I remember well, the clerics have a flame spell which bypass spell resistance (and if not, a lot of fireballs to kill his cohorts)

Great tactics, I love the fight with Yuxon

Also, nice grave digging up a 3 year old post!

Behilfet:
No enemies in this battle can be hit with less than +3 magic weapons. The only missiles I have ever found to work are the +4 Arrows of Piercing I looted off dead Drow in Upper Dorn's Deep. With a good archer (ie. lvl 20+ warrior class, 18/xx Str, 19+ Dex, +3 magic bow), you should be able to kill Behilfet with 60-80 arrows. Yes, it can be that easy. Otherwise....

All enemies do crushing damage (don't wear chain mail) and can see invisible (but they prioritize non-invisible targets):
Cornuguns - If you can't lure them away from their boss, these guys are vulnerable to frost spells. So you can take them out with 3-4 Cones of Cold. No need to melee with them or use your precious magic arrows.
Iron Golems - No need to kill these two, but you will need either 1 character to act as a decoy to lead them away from the main fight or slow them down enough so you can melee 1-on-1 with the boss for a few rounds. No magic spells seem to hurt them, but Death Fog (lvl 7 mage) will slow them down.
Behilfet - Don't bother using offensive spells on this guy, as he has what effectively amounts to total magic spell immunity. You are going to have to kill him using super-buffed hand-to-hand combat/arrows. He teleports to a new location about every 6 melee rounds or so, then casts one of several fire-based damage spells, but occasionally he will try a Hold Person as well.

I beat them with a 2-man team: a human dual Fighter/Mage lvl 6/30 and a human dual Fighter/Cleric lvl 9/24. But using the right potions, I think it can be done with just a single character (mage or cleric, your choice) about lvl 20.

What you need:
Mage
- 2 or more Haste spells/potions (just in case the spell expires in mid-fight).
- Mirror Image
- Stoneskin
- Protection from Evil
- Improved Invisibility (still bestows -4 AC even if they can see us I think?)
- 3 or more Death Fog spells (to slow down the others so you can melee with the boss alone)
- 4 cones of Cold (if you want to kill the Cornuguns first)
- Potion of Cloud Giant Strength (increases Str to 24)
- Cats Grace spell and Potion of Mind Focus (increases Dex as much as possible)
- Potion of Absorption (-10 AC vs. crushing damage)
- Lots of Healing Potions (enough to heal to full health at least once)
- Tenser's Transformation spell (doubles your HP and turns your mage into a skilled warrior)
- (optional) take any fire-based spells you like, as they will function as heal spells when cast on the magically protected cleric.

Cleric
- 2 Haste Potions (if soloing without mage)
- 4 or more Sanctuary spells (cast on self so we can safely buff/heal).
- 4 or more Resist Fire/Frost spells (cast on self till we have 150%+ protection from fire, and Behilfet's fire spells heal us instead of doing damage).
- 2x any self-buff spell whose range is "caster" (longer ranges will pop the Sanctuary spell): Prayer, Recitation, Defensive Harmony, Protection from Evil 10ft radius, Draw Upon Holy Might, etc.
- 2x Righteous Wrath of the Faithful spell (its a ranged spell so it will pop the Sanctuary, only cast if no monsters nearby)
- 4 Unfailing Endurance (just in case spells expire before the fight is over)
- 4 Heal spells or lots of Healing Potions (regain full HP)
- Potion of Giant Strength
- Potion of Mind Focus
- Potion of Absorption

As soon as the fight starts, run your team to the south edge of the room and quickly cast/quaff Haste. Stay out of the central circular area, as there are Dispel Magic traps at each of the flagstones shaped like dagger pommels. Split up from the closing enemies to safe positions and have the cleric cast Sactuary while the mage casts Death Fog. Now the cleric can buff safely as the mage baits and lures the others to run through the Fog. The slow-fog effect should buy the mage enough time to move-and-cast move-and-cast: Cone of Cold or one of his own buff spells every round or so. Meanwhile, Behilfet will teleport himself out of the fight for a while.

The Mage's goal is to bait the Golems while he buffs himself with all his spells and potions (should be buffed to about AC -25 vs. crushing damage), then Tenser transforms into a fighter (remember, you won't be able to cast spells till the transformation spell wears off, so make sure the Death Fog and Haste have been renewed at least once). Once in Fighter form, he can start shooting Arrows of Piercing at Behilfet, or engage him directly in melee.

Likewise the Cleric's goal is to buff himself with all spells and potions from his list (aslo should reach AC -25 vs crushing), and then engage a solitary Behilfet in direct melee. The Mage is going to have to keep re-positioning to stay away from the golems, so he is only going to be able to join the fight every other round or so.

If things get dicey, you can try either casting fireballs at the Cleric to heal him in combat, or otherwise the Cleric can just break off combat, run to a safe corner of the room and cast Sanctuary on himself. Then heal back to full, and return directly to the fray. The Mage should be able to easily evade the golems and quaff some Health potions, all the while peppering Behilfet with dozens of magic arrows.

My guess is Behilfet should go down at the latest before the second bell rings...

You win.