Blood Curse

You curse a creature’s blood, causing it to boil with pain. The target must succeed on a Constitution saving throw or take 4d6 necrotic damage and suffer disadvantage on Constitution saving throws for the duration. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

While the target is cursed, you can use your reaction to deal 1d6 necrotic damage to the cursed creature whenever it takes damage from any source.

At Higher Levels: When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.