I'm under the impression that the Demi-Lich at the docks can only be hit by +4 or better weapons. I killed it with the improved Mace of Disruption. I wasn't sure that was possible, so I reloaded and tested it. Korgan beserked and armed with the mace can kill it easily. It even failed a save once and was totally destroyed.
The mace is +2 (+4 vs. undead). I'm probably going to look dumb, but the +4 vs. undead makes it possible to hit the Demi-Lich, even though it's normally a +2 weapon? If so, then that mace is sweet!
The Toe