Lich lords.
I had it. I ran it. It had three glorious PC deaths that I am guitly of recounting a bit more than I probably should. Mainly because two of them were, well, mainly self inflicted.
1) The innocent one. Lich casts slay living on the well protected paladin who somehow fails to manage all his resistance rolls.
2) The slighly doughheaded one. I describe a chill shield surrounding a lich. The ubered-up monk charges to the attack and does buku damage. In those days, fire shield did double damage inflicted to the attacker.
3) This one was the most painful to watch, because it was practically suicide. A lich threw up a prismatic sphere which perturbed their efforts to do anything to it. The druid/mage who has a 35% MR from a familiar decided to chance walking into the PS to get at the lich. The player neglected to think of the fact that, in those days, every csater level below 11th was -5% to SR. Also in those days, liches were at least 18th level. 35% - (18-11)x5% = 0%. The character was zapped and disappeared as in a bug zapper.
The party somehow prevailed (I forget how), but some characters had to squander the wishes they received as awards to bring them back.