Arthur (アーサー?) is a recurring demon in the series.
King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to Medieval histories and romances, led the defense of Britain against Saxon invaders in the early 6th century. The legendary Arthur developed as a figure of international interest largely through the popularity of Geoffrey of Monmouth's fanciful and imaginative 12th-century Historia Regum Britanniae (History of the Kings of Britain).
Arthur appears as a Level 70 Battle Net opponent. Mentioning being the King of England and that he got Excalibur from the Lady of the Lake. He uses Light element demons. Beating him earns the demon Excalibur.
Persona 2: Innocent Sin
I am King Arthur of Camelot! It is a king's duty to bring his people peace and order. The power of my holy sword is yours!