Zaps
Sometimes undead monsters can resurrect themselves, such as in the Hallows End dungeon.
If you attack these monsters with a lifesteal weapon, they deal their entire health in damage to you when they ressurect, insta-killing you with huge damage. Essentially, you lifesteal negative health. Here's the combat log:
Grusk hits Jack O' Terror for 213HP! Jack O' Terror loses 213HP! Jack O' Terror dies. Jack O' Terror is resurrected! Grusk gains -37068HP. Grusk dies.
This bug has existed in the game for decades.
