Beowulf’s sword in his final battle with the dragon is named Nægling.
Nægling is described as an excellent, ancient, and powerful weapon, and it is probably the sword Hygelac gave Beowulf. Its name is related to the Old English word nægl, meaning “nail,” and it may have a parallel in the sword-name Nagelring from the Vilkina saga. The poem repeatedly emphasizes the weapon’s sharpness, brightness, strength, and venerable history.
During the dragon fight, however, Nægling breaks. The Old English passage says that the sword fails in battle and attributes the failure, strikingly, to Beowulf’s hand being too strong. Beowulf still helps Wiglaf kill the dragon, but the king receives a mortal wound and dies after seeing the treasure.
Nægling is easy to confuse with Hrunting, another famous sword in the poem. Hrunting is lent to Beowulf by Unferth for the fight with Grendel’s mother, but it cannot pierce her. Beowulf ultimately uses a giant-forged sword found in her underwater hall, not Nægling, in that earlier combat.