Divine Blood Magic

A divine caster can regain expended spell slots through a personal blood sacrifice.  The caster can injure themself causing 1 Hit Dice worth of damage (roll for damage).  The caster then regains a spell slot of level equal to the number of hit dice of damage inflicted (e.g. a cleric rolls 3d8 damage and regains a third level spell slot).  Note: this damage cannot be magically healed.  It can only be healed by a Short Rest (using Hit Dice) or a Long Rest.  Only 1 spell slot can be regained per round using this feat.