Festering Curse

Casts a long lasting curse that festers the flesh of a target creature, lowering the creature’s ability to regain hit points for the duration. The creature must succeed on a Wisdom saving throw or become cursed, reducing any healing received from any source to 0, including from Short or Long Rests. If cast on creatures higher than CR 5, the creature has advantage on the saving throw.

At higher levels, the effectiveness on stronger creatures increases. If cast at 3rd level, it affects creatures of a CR rating of 7 or lower normally, increasing by 2 CR for every spell level beyond 3rd. When cast at 6th level or higher, you can now target two creatures with one cast.