Reminds me of when one of the two primary Game Masters in our group wanted to DM a weird Dungeons & Dragons 3E game based on the original Final Fantasy but incorporating mechanics from later entries. The short version is that means healing spells hurt Undead, and a Resurrection Spell or Phoenix Down will actually one-shot an Undead, even bosses! The original Final Fantasy's early bosses include some Undead, but our DM spaced this off. We thought about saving it for the Lich, but settled for using it on his subordinate (a mini-boss), the Vampire. Which was the right call: had saved it for the Lich, the DM said he'd have had to keep it from working, but he was willing to reward us by letting it one-shot the Vampire, while having us learn that the Lich was "warded" against such tactics.
Author Notes: