The next time during the spell’s duration that you hit a creature with a melee weapon attack, your weapon pulses with a dull red light, and the attack deals an extra 1d6 necrotic damage to the target. Until the spell ends, the target must make a Constitution saving throw at the start of each of its turns. On a failed save, it takes 1d6 necrotic damage, it bleeds profusely from the mouth, and it can’t speak intelligibly or cast spells that have a verbal component. On a successful save, the spell ends. If the target or an ally within 5 feet of it uses an action to tend the wound and makes a successful Wisdom (Medicine) check against your spell save DC, or if the target receives magical healing, the spell ends.