Tar's Call

Dip your hand into hot tar and sacrifice your lifespan to end another's. Activating this spell will cause all the blood in your target's body to turn into boiling tar, killing the creature instantly, assuming it has blood to transform. This process will however permanently remove 10 from your max HP. Only a wish spell or something akin to it can cure this curse. Your blood will be darkened, becoming darker and darker the closer you get to 0 hit points.