Haven't done the Mind Flayers yet, but I've done Frikragg and the Shadow Dragon, Irenicus in the Asylum, the Sphere, etc. Hard battles usually get easy with a little advanced prep and a shift in tactics...

But for some reason, I always have trouble with beholders. I'm in Underdark now and there they are again. Was it aerial servants or spell reflections that worked last time?? hmmm...

Beholders are even easier than gibberlings if you're using one of the items that grants you near-invulnerability to them. Too cheesy for me. I'll usually take my Tank and charge them head-on while a Mage (with the Cloak of Non-Detection and the Staff of the Magi) uses a Wand of Cloudkill on the whole fight. Sure, my Tank is continually sucking down Healing Potions, but at least it's kinda fair. The Unseeing Eye quest got a lot easier after I found that the Gauths, for some reason, will not use their spells on a particular type of (low-level) summoned creature. Cool.

I find the trick with Kangaxx is to have everybody, except the guy who's actually going to kill him, have a Potion of Invisibility in their Quick Items. He goes Demi-Lich, you go Spell Immunity (or Protection Scroll), everyone else goes Gulp! Other than that, he's just another tough Lich.

The Lesser Demon Lord is only difficult if you try to kill him with weapons. I think the only weapons in the game that can hurt him are Carsomyr and the Staff of the Magi (Jerrod's Mace doesn't work, I tried it), but he's as vulnerable as anything else to a good blast of spells. I just whacked him for fun today: Korgan had an AC of -18, even without Berserking. So he & the demon pounded away at each other, neither of them really doing any damage, while Edwin, Viconia & I calmly worked his undoing. Viconia had something stupid in her "Most Powerful Vanquished" slot, so I let her apply the Finger of Death. Then I Reloaded, because this *is* an Evil party, after all.

The Illithids aren't too hard... If you've got the +2 Shield 'Harmony' which effectively mind shields you against anything. None of charm spells work and also the Illithid mind blasts don't. Either that, or I was extremely lucky when I went through the Illithid caverns.