Mordenkainen's Lost Notebook

Necrotic Curse

7-level Necromancy (ritual)

Choose a point within range. At the start of your next turn, you imbue a 20-foot-radius sphere with necrotic energy. Any creature in the area which casts a healing spell must succeed on an Intelligence (Arcana or Religion) check against your spell save DC. If the check fails, the healing spell deals necrotic damage to each of its targets instead of its normal effect. Living creatures that rest in this area do not regain hit points or spent hit dice. Undead which enter the area immediately regain 1d8 hit points. The spell can be ended by casting remove curse or greater restoration within its area specifically for that purpose.