Arcturus, better known across the world as Arthur, was a Romano-British warlord and member of the Templar Order. Using a Piece of Eden already in his position, Excalibur, Arcturus unified the warring tribes of Britannia and drove out the Saxon invaders. He then established a large castle in which to keep Excalibur, fearing that the Assassins would seek it out. He called this castle Camelot and it became his powerhouse from which he ruled Britannia and searched for more Pieces of Eden.
Eventually, Arcturus discovered that the Holy Grail, another Piece of Eden, was hidden somewhere in Britannia. He had his Templar Knights search for it many times but to no avail. Eventually, Arcturus was killed at the Battle of Badon Hill by the Assassin Odvocar, who was fighting for the the Saxons. Arcuturus had never found the Holy Grail and Excalibur was lost forever after Badon Hill.