Arthur Pendragon, most commonly known as King Arthur, is a legendary and fictional 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).
"The leading character of the Arthurian Legends, Arthur was an English hero from the Middle Ages. It is said he went on expeditions both in and outside the British Isles, all the while accompanied by his loyal Knights of the Round Table. He won multiple battles with the help of his strategist and court mage Merlin and built his kingdom. After that, he started expanding his territory and eventually conquered both Scandinavia and Rome. According to the legends, Arthur possessed a multitude of weapons, including the legendary sword Excalibur, the spear Ron, and the shield Prydwen, the latter of which depicts an image of the virgin Mary. It is believed that, among the characters in the Arthurian Legends, Arthur, Mordred, Ambrosius, and Aurelianus all existed, but there is little historical evidence."
Devil Children Black Book & Red Book (PS)
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 Sun-type demons. Beating him earns the demon Excalibur.
Devil Children Fire/Ice Book
An unused sprite for Arthur is present in the game's files.
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!