character conflict...hmm

This list may be of help

http://en.wikipedia.org/wiki/List_of_Arthurian_characters

It's all very simple. Nimue was actually a priestess training to be the next Lady of the Lake after Viviane. Morgan was, in fact, Mordred's mother. Morgause was Morgan's half sister and Mordred's foster mother (it was fairly common for high-born children to be fostered for their own protection).

I hope this helps.

With no disrespect to deliadee, it seems like those descriptions are drawn from "The Mists of Avalon," which is a very contemporary reimagining of the Arthur story.

Because the story of King Arthur is a legend, there are numerous versions of the story. Depending on whose re-telling you consult (Chritien de Troyes, Thomas Malory, Alfred Lord Tennyson, TH White), there are going to be different details.

According to most versions, the name of the half-sister who sleeps with Arthur and births Mordred is Morgause, and Morgan le Fey is a seperate villainous half-sister. But "Merlin" is certainly not the first version of the story to combine the two characters.

In Malory's version, there are multiple Ladies of the Lake, though the story never differentiates between them. I cannot remember whether Malory's version names all of the different Ladies, but in Tennyson, it is Vivian who seduces Merlin and traps him under a rock (such as the way Nimue takes Merlin out of Arthur's story and traps him behind a rock -- though of his own free will -- in "Merlin"). I believe in White, it is Nimue who does it, but I cannot remember for sure.

Your best bet is to go read up on all of the different versions yourself. I would hardly call "The Mists of Avalon" a part of the Arthurian Legend canon, but that's just my humble opinion.

Keep in mind: this is not intended to be a direct telling of the Arthur legend; it's a new retelling from a whole new perspective, so the writers are going to take liberties like that. This comes from a different direction, so certain details like that are not held sacred.