Curse of Undeath

You curse the target with the chill of the grave. The target must make a Wisdom saving throw or become cursed. While cursed in this way, their creature type changed to undead. They do not count as living, and can no longer be targeted by spells that only affect living creatures, such as cure wounds. Additionally, they no longer require air, food, drink, or sleep.

Additionally, the acute stop and start of bodily functions can cause physical trauma. When the creature becomes cursed, and again when the curse ends, it must succeed on a Constitution saving throw. On a failed save, the creature suffers 1 level of fatigue, plus 1 additional level for each increment of 5 it fails by.

Dispel magic has no effect on this spell, but remove curse or other similar abilities can remove it. Additionally, any spell that restores life removes this curse. The spell has no effect on undead or constructs.

At Higher Levels. If you cast this spell using a spell slot of 4th level or higher, the duration is concentration, up to 10 minutes. If you use a spell slot of 5th level or higher, the duration is 8 hours. If you use a spell slot of 7th level or higher, the duration is 24 hours. If you use a 9th level spell slot, the spell lasts until it is dispelled. Using a spell slot of 5th level or higher grants a duration that doesn't require concentration.