Void Dismemberment

You touch a creature and stimulate its natural dying ability. The target takes 11d8 + 15 necrotic damage. For the duration of the spell, the target loses 1 hit point at the start of each of its turns (10 hit points each minute).

The target's body will lose one member (fingers, legs, tails, and so on), of the casters choice, which will fall off from decay after 2 minutes. If you have the severed part and hold it to the stump, the spell instantaneously causes the initial damage. This body part will magically find its way back to its owner after 30 days, or can be put back by the caster.