Dragnov's Arcane Absorption

You use your Necrotic powers to transform the life of others into magic to fuel your spells.

Make a melee spell attack against a creature within your reach. On a hit, the target takes 15d6 necrotic damage, and you regain one spell slot of a level equal to one tenth the amount of necrotic damage dealt. Until the spell ends, you can make the attack again on each of your turns as an action.