Mark of death

As a bonus action, you mark a creature for 1 minute. When you hit that creature with an attack, you deal an extra 2d6 necrotic damage and regain hit points equal to the necrotic damage dealt. If the creature is reduced to 0 hit points by this feature, you also gain temporary hit points equal to the necrotic damage dealt. Once used, you can’t use this feature again until you finish a short or long rest.