Arthurian Legends

The Arthurian legends are an entire extensive mythology and folklore named after their pivotal character, the legendary King of Britain Arthur, and centered around his reign and his Knights of the Round Table.

Principles
Like with other folk heroes, there may be historical truth to the myth, the historical Arthur may having been a Romano-British dux bellorum ("leader of battles"), a warlord fighting on behalf of the British kings the invading Anglo-Saxons after the fall of the Western Roman Empire.

Other elements of the Arthurian legend originally had their roots in Cornish and Welsh legends, where he and his men, often with magic items and powers of their own, appear as adventurers facing not only normal human foes but also fantastic creatures like giants (men and beasts) and witches. Due to this more fantastic strand of the myth with ties to Celtic Mythology, some scholars believe Arthur began as a mythical folk hero who was then historicized into the Briton/Anglo-Saxon conflicts.

Following the Christianization of the British Isles, more elements not present in the original legends were added, thanks to writers such as and, reflecting the new culture of the Britons: the themes of chivalry, courtly love, elements from Christian myths like the Holy Grail, etc.

Background
As Arthurian legends evolved over the centuries and spread across Europe, many characters faded from existence or were replaced with local variations. For example, the Knights of the Round Table, introduced later, did not include any of the old knights who had initially supported Arthur. Another example is how his full sister Queen Anne became the mother of Mordred (who was not originally related to Arthur); she was eventually replaced by half-sister Morgause, who kept the blood-tie but is a different character entirely.

St. Germain Arc
After the High Priest, Nephthys and Niang-Niang manage to manifest in Academy City in order to carry out their work, Nephthys mentions how King Arthur had a twin sister named Queen Anne, and a shield to match his sword.

Later, while on the rooftop garden of the Dianoid, St. Germain tells Kanou Shinka of the Arthurian legends, which are closely related to her plans, mentionning different characters associated with the myths, but especially focusing on how Galahad, the son of Lancelot and the knight who ultimately found the Holy Grail, surpassed King Arthur by having both a holy sword and a holy shield. She reveals that she is looking for the one who can wield Queen Anne's Shield, the counterpart of Excalibur, and the only one who can do that is someone who is genetically close to the mythical twin sister of King Arthur, Queen Anne, which in this case is supposedly Shinka. In the end, she tells Shinka that, because he was chosen by the shield, the St. Germains would serve him as a king, comparing her role to that of a man in the Arthurian myths who mastered all sorts of magic, but only supported the king’s rule without ever thinking of becoming king himself, clearly referencing the legendary magician Merlin.