Potion of Necrotic Poison

A creature subjected to this poison must succeed on a DC 16 Constitution saving throw or take 2d6 necrotic damage and become Poisoned. The Poisoned creature must repeat the saving throw every 24 hours, taking 3 (1d6) poison damage on a failed save. Until this poison ends, the damage the poison deals can’t be healed by any means.
Who would create such a thing, who knows what the long-term effects are...