Verdorren

You cast a dark curse on a creature of your choice, causing them to take 1d10 necrotic damage at the beginning of their turn until you choose to dispell it or until you are downed or killed. From them on, the creature must roll a wisdom saving throw at the beginning of their turn. If it fails, they take an additional 1d10 necrotic damage at the start of their turn.

(ex: they fail the save once, now they take 2d10 damage at their turn start. The saves are only to prevent the damage from increasing, not to prevent it as a whole)

 If you use this spell on a creature that already has the curse, they will have to make a wisdom saving throw immediately and if it fails, they will take an additional 1d10 damage at the start of their turn)