King Arthur was adventuring in the forest when the sorceress Annoure spotted him. She wanted him to stay with her in her castle, so she invited him inside.
WAIT! He is our KING!
Ah, the legendary Excalibur. I, Arthur, King of the Britons, will rule all with it at my side!
Annoure promised Arthur anything he wanted if he would stay with her, but he knew her wicked ways. He refused, and she imprisoned him. When she returned and Arthur still refused, she released him.
However, King Arthur was unaware that the path Annoure lead him on brought him to Sir Pellinore, a brave and fierce knight who would challenge Arthur to a duel. Arthur, loving adventure, would accept.
Arthur was fairly beaten in battle both on horseback and off, but just as Sir Pellinore was about to end his life, Merlin the wizard appeared to save the King by putting Sir Pellinore into a deep sleep.
Arthur was pleased to survive the encounter with Sir Pellinore, but would not return home with Merlin without his sword, which had been destroyed in battle. Merlin took him to a lake to retrieve the mythical sword, Excalibur, which he returned to his knights with.