Arthurian Legends

Arthurian legends is the name given to the entire extensive mythology and folklore named after its 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.

Uses of Arthurian legends in the story

 * Anne: King Arthur's sister's name in Geoffrey of Monmouth. Called Morgause and other variations in other versions, she is mostly known for unwittingly sleeping with her own brother, thus becoming the mother of Mordred, King Arthur's killer.
 * A magical shield that supposedly belonged to her, Queen Anne's shield, is the magic item central to the conflict in the 12th Shinyaku Toaru Majutsu no Index Light Novel.
 * Arthur Pendragon: Legendary king of Britain and central character of the Arthurian legends. Pulling out a sacred sword from a rock to prove he was the rightful heir to the throne. he ruled Britain into a golden age with the wizard Merlin at his side, and assembled the Knights of the Round Table to serve as paragons of chivalry. His reign comes to an end when he kills and is killed by Mordred, his own traitorous son/nephew.
 * The legendary king is mentioned throughout the 12th Shinyaku Toaru Majutsu no Index Light Novel, especially in relation to his twin sister Queen Anne.
 * Constantine: In Geoffrey of Monmouth, Constantine III of Dumnonia becomes the king of Britain as King Arthur's rightful heir after his death.
 * He is briefly mentionned by St. Germain as a distant blood relative of King Arthur.
 * Elaine: The daughter of the Fisher King, the guardian of the Holy Grail, who fell in love with Lancelot when he came to the Holy Grail Castle on his quest to retrieve it. She rapes him in his sleep, and gives birth to Galahad.
 * She is briefly mentionned by St. Germain as the mother of Galahad.
 * Excalibur: The legendary sword of King Arthur. Some versions say that Arthur pulled Excalibur from a stone (or anvil) to prove his right to be king, while other versions say that the sword from the stone was not Excalibur, but a different sword, and Arthur instead was given Excalibur by the Lady of the Lake.
 * According to St. Germain, Queen Anne's Shield is the perfect counterpart to Excalibur.
 * Galahad: The strongest and most perfect knight, he is the only one who managed to attain the Holy Grail out of all the Knights of the Round Table.
 * St. Germain explains Galahad's victory as him possessing both a holy sword and a holy shield, whereas Arthur only had Excalibur. Using this story, St. Germain concludes that Queen Anne's shield exists,
 * Holy Grail: The cup which the Son of God supposedly drank from at the Last Supper and/or the cup used by Joseph of Arimathea to capture the blood of Christ at the Crucifixion.
 * Index cites it as one of the the limits on how magicians are capable creating substitutes for ceremonies using modern materials.
 * The quest for the Holy Grail in Arthurian legends is briefly referenced by St. Germain, and how Galahad was the one to reach it.
 * Knights of the Round Table: King Arthur's champions and chief companions, who later developed into knights-errants going on fantastic quests and defending the weak.
 * The Thirteen Knights of the Roman Catholic Church are apparently named after the Knights of the Round Table, such as Percival (Parsifal) and Lancelot.
 * Lancelot of the Lake: King Arthur's most famous knight, who had many famous exploits, but is mostly known for falling in love with King Arthur's wife Guinevere
 * Mentionned by St. Germain as being the father of Galahad.
 * Merlin: A great magician and the trusted advisor and surrogate parental figure to King Arthur.
 * While not explicitely named, he is certainly the man described by St. Germain as a man who mastered all sorts of magic, but never thought of becoming king himself, only supporting the king’s rule.
 * Spear of Longinus: The spear which supposedly pierced the Son of God' side during the Crucifixion, reputed to have all kinds of special powers.
 * Cited by Index twice, first to explain how strong her Walking Church is, then as one the relics that cannot be substituted by magicians using the Idol Theory.
 * The Thirteen Knights of the Roman Catholic Church mass produce substitutes of the holy spear in the form of Longinus Replica.
 * The Maiden of Versailles wields Durandal, a legendary sword said to be made from a shard of the holy Spear.