Who Is Sir Accolon of Gaul?

Sir Accolon of Gaul is a knight from Gaul (roughly modern-day France) and the lover of Morgan le Fay. Through Morgan's scheming, he ends up fighting King Arthur in a duel to the death.

In Episode 5, Morgan gives him the real Excalibur and the scabbard that keeps its wearer from bleeding, and he fights in place of Sir Ontzlake. He does not know his opponent is the king. Arthur, armed only with a fake sword, is driven to the brink, but Nimue's magic makes Excalibur fall from Accolon's hand, and Arthur, regaining sword and scabbard, wins the fight.

Defeated, Accolon learns that his opponent is the king and confesses that Morgan had plotted to kill Arthur and make Accolon king. He dies of his wounds a few days later, and Arthur sends his body back to his sister Morgan.