Through a series of blood rituals you have developed a dark and subversive method for pushing your magical spellcasting abilities. You can use this feat to cast a spell from your hit dice.
Up to a maximum of five spell casting levels you can spend your hit dice to cast a desired spell you already know. After casting the spell, you roll the hit dice you expended and subtract this total from your maximum hit point total.
To recover your maximum hit point total, you must perform a long rest. The feat can be used as much as is required or until you reduce yourself to zero hit points. If your Blood Sorcery reduces you to zero maximum hit points, only a revivify or resurrection spell can bring you back to life.