Just go to Christopher Bruce’s Arthurian dictionary at http://www.celtic-twilight.com/camelot/bruce_dictionary/index.htm . This will give you more accurate information than people who have mostly or only read modern novels and seen modern films. It is not entirely free of error, but far less absurd than the answers you have been getting.
Morgain la Fay is not Mordred’s mother in ANY medieval story.
Making her Mordred's mother is an invention of modern novelists. “The Mists of Avalon'' is a novel which uses some medieval Arthurian traditions and the inventions of the author. But so are other modern novels.
For Mordred's begetting in the medieval romances, see http://www.lib.rochester.edu/camelot/teams/yosqfr.htm, line 90 and following, for one version. See http://members.terracom.net/~dorothea/baladro/Chapter18.html and http://members.terracom.net/~dorothea/baladro/Chapter19.html for the Post-Vulgate version. In the “History of the Holy Grail” we are told:
“And the king fathered him [Mordred] with his sister one night, when he thought he was laying with the beautiful woman from Ireland. When he recognized his sister and realized he had lain with her, both of them were grief-stricken and repented."
The stories in each case differ, but the sister is the mother of Gawain, and is not Morgaine la Fay who is never connected to Mordred, except as one of his aunts. Indeed in some tales Morgaine is not even Arthur’s sister. For example, in the story of Huon of Boudeaux, Morgaine is the the mother of the fairy king Auberon by the famous Julius Caesar. In the “Perceforest” Morgaine lives in Britain long before even the Roman invasion. In Robert de Boron’s “Merlin”, Morgaine is the bastard daughter of the Duke of Tintagel, and therefore only Arthur step-sister, not his half-sister.
In earlier tales Mordred is simply Arthur’s nephew and Gawain’s full brother. That Mordred was really Arthur's son and therefore only a half-brother to Gawain first appears in the “Prose Lancelot” , but no details are given about how he was begotten, save that Arthur had a dream of a dragon following the begetting.
The Lady of the Lake is the woman who betrayed Merlin and raised Lancelot as a child, and has nothing whatsoever to do with the fay who gave Arthur his sword in the “Post-Vulgate Merlin''. Malory, in retelling the story, alone calls this fay the “Lady of the Lake”, but since she dies soon after, even in Malory she is not identified or confused with the main Lady of the Lake whom Malory also introduces.
That Merlin is a druid is another modern invention.
Camelot is only one of many cities in which King Arthur held court in various romances.
Medieval accounts are mostly as much inventions as are modern novels. But they are at least the accounts on which modern novels claim to be based, though often falsely. Modern novelists have the same right and liberty as medieval writers to invent and modify. And their readers have the same right to believe that what they read is “true”. But they don’t have the right to declare, without source, that particular inventions are the “original accounts” without being opposed.
If you want to indicate something from a modern novel, then you should cite that novel directly. And the same for medieval works as often they also do not agree with one another.