Debt to the Deathless

You hold the coins in your hand and drip blood onto them from the vial, watching as they fade away when the ruby liquid hits their shining surface. The payment is well worth the debt to be collected. Choose any number of creatures that you can see in range. Each of those creatures must make a Constitution saving throw, losing 12d4 hit points of necrotic damage on a failed save, or half as much on a successful one. Afterwards you gain a number of temporary hit points equal to half the damage dealt this way.