Ballet of Blood

You have a +3 bonus to attack and damage rolls made with this magic weapon. In addition, when you damage a creature with this weapon, the target can't regain hit points until the start of your next turn. When you hit with an attack using this weapon, the target takes an extra 2d6 slashing damage.

When you attack a creature with this weapon and score a critical hit on the attack roll, the creature must make a DC 19 Constitution saving throw. The creature takes an additional 20d6 damage on a failed save, or half as much damage on a successful one. A creature is immune to this effect if it is immune to slashing damage or doesn't have blood. Once this property of the sword has been used three times, it ceases to function until the next dawn.

Proficiency with a Longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, Damage: Slashing, Damage, Combat, Versatile, Sap