Umbral Consumption

You manifest a small Void in your hand. Make a Melee Spell Attack. On a hit, the targeted creature takes 2d12 necrotic damage, healing yourself for half the damage dealt. For the spell's duration, you can use your action to cause the creature to take 1d12 additional necrotic damage. The spell ends if you use your action to do anything else, or if the creature is no longer within 30 feet of you or if you lose line of sight to it.

Casting at higher levels: When cast with a spell slot of 4th level or higher, the initial damage of this spell increases by 1d12.