The legend of King Arthur varies widely in its many retellings, but generally involves a young man prophesied to pull a sword from a stone and who for that reason becomes king. He then receives the legendary sword Excalibur from a mysterious being known as the Lady in the Lake, and forms a heroic group of knights known as the Knights of the Round Table.
Very few Arthurian legends are exactly the same, but generally, Arthurian legend makes Arthur Arthur Pendragon, son of Uther Pendragon, an aspirant king who ultimately fails to unite Britain and leaves his infant son in the care of the knight Sir Ector. The wizard Merlin is Arthur's mentor and adviser throughout his reign. In some versions of the tale, Merlin knows of Arthur's destiny before he pulls the sword from the stone; in others, he learns of Arthur's destiny when he pulls the sword.
His wife, Queen Guinevere, involves herself in an affair with Arthur's bravest knight, Sir Lancelot. Many of the knights engage in independent adventures which are part of the Arthurian legend, and sometimes a search for the Holy Grail, an object in Christian folklore said to be the cup Jesus Christ drank from at the Last Supper before his death. Arthur, in the end, kills and is killed by his son Mordred, born to him by his half-sister Morgan le Fey.
Historically based Arthurian legends put King Arthur as a Celtic or Romano-British king fighting against Anglo-Saxon invaders, though there is little reliable evidence for either of these interpretations.