Prime Materials: Shadowfang, a magic dagger for D&D 5th Edition

Shadowfang
Magic weapon (dagger), rare (requires attunement)

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

In addition, when you deal damage while attuned to the dagger, as a bonus action you may utter a command word and gain 20 temporary hit points.  This ability may not be used again until you complete a short or long rest.

The Queen of Terror, Coaxoch Ixklurio, presented Shadowfang to Jafar Qane, a Golden Legionnaire of Amn for betraying his entire company to the maztican vampire.