If it bleeds, we can kill it.

Increase your dexterity score by 1. Once per turn when you hit a creature with an attack you can have that creature roll a constitution saving throw (DC=8+The attack modifier of the attack that causes the save) if the creature fails the save apply a fatal wound to the target. A creature can only have 3 fatal wounds on them at one time. A creature that starts its turn with a fatal wound takes 1d6 necrotic damage per fatal wound at the beginning of each of the creatures turns. A creature can use its action to make a medicine check DC10 to remove all fatal wounds on 1 creature.