Curse of the Dark Heart

You utter an ancient curse that targets the heart of a creature within range. The target must make a Wisdom saving throw. On a failed save, the curse takes hold, and the creature's heart is consumed by darkness. The creature takes 3d6 necrotic damage at the start of each of its turns for the duration of the spell, and its hit point maximum is reduced by an amount equal to the damage taken.

The curse can be removed by a remove curse spell or similar magic.

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.