Stulorne Blades are blades that are not forged using sorcery. They appear blunt to the eye but in reality they are razor sharp.
Two thugs Dagr and Ebor asked the sorcerer Cylferth to get them the Stulorne Blades in order to use them in a tournament in Camelot and get their revenge on Arthur. While Merlin was cleaning their room, he accidentally cut himself with one blade. The Stulorne Blades led Merlin, Gaius, and Gwaine to discover the Knight's true identity. During the tournament Gwaine killed Dagr and Ebor using these swords (Gwaine).