Shamshir e Zomorrodnegar

Shamshir-e Zomorrodnegār (Persian: شمشیر زمردنگار, 'the emerald-studded sword') is a sword in the Persian legend Amir Arsalan. The witch mother of a hideous horned demon called Fulad-zereh used a charm to make his body invulnerable to all weapons except this specific sword.

Shamshir-e Zomorrodnegār originally belonged to King Solomon, and was carefully guarded by Fulad-zereh, not only because it was a valuable weapon, and indeed the only weapon that could harm the demon, but also because wearing it was a charm against magic. A wound inflicted by this sword could only be treated by a special potion made from a number of ingredients, including Fulad-zereh's brains.