At the very end, hidden underground is a shadow (the undead creature). The fight went badly for the party - all the warriors were helpless from strength drain, no magic weapons, magic weapon spells cast and used, and the shadow was on 1hp. The wizard was out of spells, the cleric only had 0-level spells left, and (not knowing it was on 1hp) used a cure minor as a touch attack and killed it.