Blood Mark

You choose a creature you can see within range and attempt to mark it as your blood quarry. The creature must make a Constitution saving throw or be marked by you for the duration. Until the spell ends, on each of your turns, you can as a bonus action expend any number of available hit dice and deal that much necrotic damage to the marked creature. If the target drops to 0 hit points before this spell ends, you can use a bonus action on a subsequent turn of yours to attempt to mark a new creature.

Creatures that don't have blood, such as plants, constructs and some undead (determined by DM), cannot be targeted by this spell.