Character Analysis
Mordred (the baby of the family) is the main villain of the novels. He's Arthur's son and nephew, the ill-fated spawn of an accidental incestuous fling between Arthur and his half-sister. From the very first mention of Mordred in the text, we know he's going to be up to no good: "It was called Mordred" (Q.14.17).
This foreshadows his evil nature; he's not even human—the narrator refers to him as a thing, an "It." His name is in all caps in that family tree at the end of The Queen of Air and Darkness, so you can't really get much more portentous than that. And what a name! It combines two terrible things: "mort" is French for "death," and "dred" is pretty dang close to the English "dread."
One May Smile and Smile and Be a Villain
His description tells us a lot about him as well. It's worth looking at the entire thing. Check it out:
He was a thin wisp of a fellow, so fair-haired that he was almost an albino: and his bright eyes were so blue, so palely azure in their faded depths that you could not see into them. He was clean-shaven. It seemed that there was no part of him which you could catch hold of, neither his hair, nor his eyes, nor his whiskers. Even the colour had been washed out of him, it seemed, so as to leave no handle. Only, in the skeletal, pink-face, the brilliant eyes had crow's feet round them—a twinkle which you could assume to be of humour, if you liked, or else of irony, or merely of screwing up those sky-blue pupils so as to look far and deep. He walked with an upright carriage, both ingratiating and defiant—but one shoulder was higher than the other. He had been born slightly crooked—a clumsy delivery by the midwife—like Richard III. (K.27.2)
Where do we even start? Coldness just radiates from this guy: he's pale and washed out, and even his eyes are pale like a cold, blue sky. The rest of the description (the bare cheeks, the no-color, the thinness of him) suggests that you can't get a handle on him, that he's slippery and dishonest. Plus, he's born "slightly crooked," and he's hunchbacked like the famous Shakespearean villain Richard III.
Even though he's clearly a villain (and goes a bit crazy at the end of the novels), we can still feel a bit of empathy for this multi-layered character. For one, he was raised by an abusive mother who, in Guenever's words, "ate Mordred [...] like a spider" (C.11.58). Arthur even speculates that Mordred might have been in love with her.
And then the guy also has to live with the knowledge that his own father tried to kill him when he was a baby—and in the process killed hundreds of babies. This is bound to make anyone a bit messed up.
Mad Power Grab
As he gains power at Court, Mordred becomes vain and outfits himself in ridiculous style: shoes with long, pointed toes and chains that attach from the toes of the shoes to a belt around his waist (K.36.3). He wears this, though, with all the sly irony of a modern-day hipster: "they were a satire on himself" (K.36.3).
Aside from this, he takes up a leadership role with a popular uprising, and calls his men the Thrashers. They end up being against Arthur, and when he goes off to fight Lancelot Mordred makes his power-play for the throne.