In Malory's Le Morte D'Arthur, when King Arthur entrusted Excalibur into Morgan le Fay's care, she had a duplicate made; the real scabbard was then passed from her to her lover Accolon /ˈækəlɒn/.
Morgan then tricked Arthur and Accolon into fighting each other, Accalon using the real Excalibur while Arthur used the duplicate. During the battle Arthur's sword broke; he quickly realized this was not the real Excalibur and that he had been betrayed. Rather than giving up, Arthur continued to fight with what was left of his shield. Nyneve, the Lady of the Lake, arrived and used her magic to cause Excalibur to fly from Accolon's hand. Arthur then wrestled the scabbard back and dealt Accolon a mortal wound. Accalon died four days after receiving the battle-wound from Arthur.
The scene of Accolon's battle with Arthur is included in Marion Zimmer Bradley's The Mists of Avalon, though with the role of Nimue omitted. In Bradley's interpretation, Morgaine and Accolon's aim was to restore the pre-Roman Celtic Pagan religion, threatened by the aggressive advent of Christianity.