Blood Magic 5e

Prerequisite: The ability to cast at least one spell
You have learned to use your blood to recover expended spell slots. None of the slots can be 5th level or higher.
As an action you can sacrifice a number of hit points equal to the maximum value of your greatest Hit Dice multiplied by the level of the spell splot you want to recover. You can’t regain the hit points lost in this way, even magically, until you finish a long rest.