The scabbard of Excalibur, “heavy of gold and precious stones”, was, in Merlin’s opinion, worth ten of the sword, because as long as a fighter had the scabbard upon him, he would lose no blood, no matter how severely wounded. The importance of the scabbard is an argument for making Excalibur the sword given by the Lady of the Lake, since it is more difficult to account for a scabbard belonging specifically to a sword that appeared sheathed in stone and anvil.
Morgan stole this scabbard and threw it into a convenient body of water fairly early in Arthur’s career.
In the fifteenth-century Catalan romances Tirant Lo Blanch, Excalibur seems to possess a kind of oracular magic: gazing into his great sword enables Arthur to give every questioner an answer replete with the wisdom of medieval courtly philosphy. This, however, occurs in a passage that surely describes an elaborate and presumably rehearsed masque.
When Gawaine fought the magician Mabon over the fairy Marsique, she obtained the scabbard for him but it subsequently disappeared.
Sir Thomas Malory does not name the sword in his Le Morte d’Arthur. In the early Welsh story of Culhwch and Olwen, the sword is called Caladvwlch, which can be linguistically linked with the magical sword Caladbolg (derived from calad – ‘hard’ – and bolg – ‘lightning’), a sword borne by Irish heroes, and in particular Cú Chulainn. Geoffrey of Monmouth calls the sword Caliburnus, and so derives the Excalibur of the romances.