Item description:

If Life 3 gets cast on an Undead enemy, it will not usually revive them because Undead enemies do not get revived by Life spells; they get killed by them. However, Undead enemies do automatically revive themselves when struck by weapons that kill with an “X” animation. Then Life 3 would kick in, even though the enemy is still technically alive, and kill them. This patch exempts all Undead enemies from any effects of Life 3 spells.