The dwarves Dvalin and Durin take revenge on their captor by cursing the sword Tyrfing
Poor little dwarves(( In his day Dvalin forged golden hair for Loki and made many other marvellous things. A regrettable accident, by which he and his friend became the prisoners of Sigrlami, was resolved, as so often happens, in a manner unexpected by the victor. Dvalin and Durin took their revenge on their captor by cursing the weapon: the Tyrfing they forged was the sharpest sword in the world, cut through iron and stone and always brought victory, but could not be returned to its scabbard without being bathed in warm blood, and in the end it destroyed its owner.