Amulet of Tempus

This iron amulet bares the sword and flame of the god Tempus. Only a true believer may touch it or be burned. Once per long rest a creature of your choice that damaged you is momentarily surrounded by Radiant Flames. This creature must make a Dexterity saving throw. It takes 2d10 Radiant damage on a failed save, or half as much damage on a successful one.