The legend of King Arthur is best summarized as the story of a young boy who pulls the sword Excalibur out of a stone and becomes the King of England. His idealism spawns the Knights of the Round Table, but his jealously brings down his reign.
As a young boy, Arthur is brought up by the wizard Merlin, away from his parents and unaware of his lineage to the crown. He pulls Excalibur out of a stone, a feat that was thought to be impossible, and is crowned King of England. He falls in love with a woman named Guinevere and makes her his queen. He drives the Saxon threat out of the realm and brings the best knights of Britain to Camelot, his castle, and calls them the Knights of the Round Table. Although there are many quests he and his knights endure, the most idealistic is to find the Holy Grail and bring it to England. While Arthur is never able to find the Grail due to his birth being in sin, Sir Galahad, one of his knights, does.
During his marriage to Guinevere, he finds that she is secretly in love with one of his knights, Sir Lancelot. When he discovers their affair, his jealously leads him away from Camelot to pursue the lovers into France. While he is away, his nephew Mordred claims the castle for himself. During the resulting battle for the crown, Arthur is wounded. According to the legend, he throws Excalibur into a lake and leaves England for the magical Isle of Avalon where he plans to stay until cured. He vows to return to England one day to lead his people.