Anna(?), Belicent, Bellicent, Margause, Morawse, Mordads(?), Morgawse
One of the three daughters - seemingly the oldest - of Igraine and Gorloïs, Margawse was wedded to King Lot at the same time that her mother was wedded to Uther Pendragon, her sister Elaine of Tintagil to King Nentres, and her other sister, Morgan, was put to school in a nunnery.
Although her husband was one of the chief rebels against Arthur, the Vulgate tells us that Margawse was a staunch supporter of the young High King, enocuraging those of her sons who were old enough, especially Gawaine, to join Arthur's side. She herself rode down through dangerous territory to join Arthur's side in person, having several adventures on the way. Malory, however, insinuates that lot sent his wife to Arthur's court as a spy.
And thither came to [Arthur], King Lot's wife, of Orkney, in manner of a message, but she was sent thither to espy the court of King Arthur; and she came richly beseen, with her four sons, Gawaine, Gaheris, Agravaine, and Gareth [who must still have been a babe in arms], with many other knights and ladies. For she was a passing fair lady, therefore the king cast great love unto her, and desired to lie by her; so they were agreed ... So there she rested her a month, and at the last departed.
At this time, at least in Malory's account, she did not know Arthur was her half-brother. How she reacted to Arthur's seizure of her youngest born, Mordred, along with other lords' sons that were born at the same time, in order to destroy them, Malory does not record, though he does note it as Lot's motive for the second rebellion.
Her husband killed in this second rebellion, Margawse apparently remained north, governing Orkney and raising her youngest sons. When Gareth was old enough, she sent or allowed him to go to Arthur. After something more than a year, she followed him, arriving at Arthur's court while Gareth was absent on his first round of knightly adventures.
And as they sat at the meat, there came in the Queen of Orkney, with ladies and knights a great number. And then Sir Gawaine, Sir Agravaine, and Gaheris arose, and went to her and saluted her upon their knees, and asked her blessing; for in fifteen year they had not seen her.
She had somehow learned how Gareth had spent his first year at court.
Ah, brother, said the Queen unto King Arthur, and unto Sir Gawaine, and to all her sons, he did yourself great shame when ye amongst you kept my son in the kitchen and fed him like a poor hog. Fair sister, said King Arthur, ye shall right well wit I knew him not ... meseemeth ye might have done me to wit of his coming, and then an I had not done well to him ye might have blamed me. ... Sir, said the Queen of Orkney ... wit ye well that I sent him unto you right well armed and horsed, and worshipfully beseen of his body, and gold and silver plenty to spend. It may be, said the King, but thereof saw we none.
Margawse's relations with her brother and his court seems to have been cordial. Although by now middle-aged, she was still beautiful enough that Sir Lamorak, who became her paramour, was ready to defend her beauty against that of Guenevere. Lamorak being the son of Pellinore, the man who had dealt King Lot his death wound, Margawse's new affair did not please her sons. She accepted their invitation to a castle near Camelot, and there she and her lover arranged a tryst. Her son Gaheris, watching his chance, came to their bedside and struck off her head. Learning it,
the king was passing wroth, and commanded him to go out of his court.
T.H. White (who transfers her murder to Agravaine) gives her at least enough grasp of sorcery to conjure Arthur into bed with her by enchantment. I do not recall finding any indication in Malory or in the Vulgate that Margawse was an enchantress; it has been suggested, however, that, although definitely two individal characters in the sources on which I have concentrated, Morgan and Margawse originally were the same character, and became split when some scribe got confused with the case endings of a language not his own. Most modern romancers put the blame for Mordred's conception entirely upon Margawse, whom they usually make aware of the incest at the time - Stewart's popular version, which for some reason changes Margawse's own parentage to make her not a legitime daughter of Igraine and Gorloïs but a bastard of Uther, is particularly hard on her, stripping away even the shadow of self-justification for the act that other romancers allow her.
In my opinion, all this is part of the modern whitewashing of Arthur. (Notice that there is more suggestion of underlying affection than of smoldering hatred and resentment when brother and sister bicker about Gareth, as Malory records the scene.) Tennyson, unable to charge his Arthur with incest, or even adultery, on any pretext whatever, named the wife of Lot and the mother of Gawaine, Gareth, and Mordred Bellicent (Belisent), perhaps to avoid any identification of her with the lusty and accidentally incestuous (but also spirited and generous) Margawse.
While Chrétien de Troyes does not mention Margawse by name (he does several times mention Morgan; if the two began as one character, she might not yet have split), he does tell us that Lot's queen and Gawaine's mother - the woman whom later romancers were to identify as Margawse - followed her mother Queen Ygerne (Igraine) to the Rock of Canguin and there gave birth to a daughter, Clarissant. (Chrétien's translators Owen and Cline give notes respectively naming Ygerne's daughter Anna and Morcads (Morchades).)
Gawaine is astonished to hear who the queens of Canguin are, since he had believed Ygerne gone for sixty and his own mother for twenty years. The evidence that Canguin may be a branch of the Afterlife could facilitate combining Malory's version of Margawse's death with Chrétien's happier ending for Gawaine's mother; such a combination would make Sir Lamorak Clarissant's probable father.
By the way, has anyone noticed that the two queens and princesses of Canguin neatly form the venerable Trinity of Maiden, Mother, and Crone?