Devouring Blade

Requires the Pact of the Blade feature.

You pour the blood of a creature onto your pact weapon. Until the spell ends, when your pact weapon hits a creature of the same type as the blood used to cast this spell, you can roll one of the weapon’s damage dice one additional time and add it to the damage of the attack. You also regain a number of hit points equal to half the damage dealt. The spell ends early if you cast this spell again or you use your Pact of the Blade feature again.