You gain a +1 bonus to attack and damage rolls made with this magic weapon.

If you score a critical hit with an attack made with this weapon, the target takes an additional 2d6 necrotic damage, and you gain temporary hit points equal to the additional damage. Constructs and undead are immune to this effect.

When you hit with an attack using this weapon, you can spend a bonus action to force the target to make a DC 15 Constitution saving throw. On failure, the target takes additional necrotic damage equal to its Hit Die and you gain hit points as though you spent a Hit Die. Constructs and undead are immune to this effect. The dagger can't be used this way again until the next dawn.