Devil's Due

You absorb a measure of a creature's suffering and escaping vital essence. Expend and roll one Hit Point Die. You regain a number of Hit Points equal to the number rolled plus your spellcasting ability modifier.

If the creature took damage from a Critical Hit, double the number of Hit Points you regain.

Using a Higher-Level Spell Slot. You can expend one additional Hit Point Die for each spell slot level above 1.