Here's how Wolfram describes her, in the recent (2004) translation by Cyril Edwards:
She was called Cundrie; her byname was Surziere [i.e., the magician or sorceress]…. A bridal cloth from Ghent, bluer even than lapis lazuli, that downpour on joy had donned. It was a well-cut cape, all in the French style. Beneath, next to her person, she wore fine furs. A peacock-feather hat from London, lined with cloth-of-gold—the hat was new, its ribbon not old—hung at her back…. A plait crossed the hat and dangled down from her, as far as the mule [she was riding]. It [the plait] was so long, and black, tough, none too lustrous, soft as a pig’s back hair. She was nosed like a dog. Two boar’s teeth stuck out from her mouth, a good span in length. Each eyebrow thrust, plaited, past her hair-band…. Cundrie had ears like a bear’s….Her countenance was hairy….There are other details in Wolfram's description, but those are the ones I tried to include in my drawing, if only through the merest suggestion. (In a head-on view, it was difficult to manage her braid of coarse hair hanging across the fine hat that dangles against her back, though I did at least arch up the tip of the peacock feather to be glimpsed over her shoulder.)
A note or two about Cundrie. Wolfram borrows the basic character, including her initial messenger function and a number of her ugly features, from Chrétien de Troyes's late twelfth-century romance Le conte du Graal (Perceval), the original literary account of the Grail. Wolfram expands her role and her context, however, in his additions (and conclusion) to Chrétien's unfinished work, and Wolfram provides her with a name. Both authors agree on an unusual point, however: while she is quite hideous to behold, she is also a model of upright virtue.
This point is unusual because the prevailing approach to appearances in medieval romance is to associate beauty with goodness and virtue while ugliness is associated with baseness and evil. The hideous Cundrie in fact arrives to throw cold water on the joy felt at Arthur's court upon the return of Parzival, celebrated not only as a paragon of knighthood but as a beautiful specimen of young manhood. Cundrie announces that this seeming great guy is in fact a bit thick and unfeeling, and he has had the misfortune to be thick and apparently unfeeling under circumstances that threaten to doom a whole populace. Oops!
So, yeah: looks can be deceiving. Interestingly, this trope recurs in other Grail narratives. In the thirteenth-century Old French prose Quest of the Holy Grail (and in Sir Thomas Malory's fifteenth-century Middle English adaptation, The Tale of the Sankgreal), Perceval is one of the three knights who successfully "achieve" the Grail quest, along with Lancelot's kinsmen Sir Bors and the impeccable Sir Galahad (and I'm using that adjective in its theological sense as well as its ordinary sense). While the virginal Galahad is impervious to sexual temptation (though he has a strong bond with Perceval's equally virginal sister), Sir Bors and Sir Perceval both get tempted toward error in instructively different ways that have to do with what meets the eye.
Perceval is the object of a would-be seduction by a devil in the guise of a beautiful woman; he resists just in time to avoid damnation, at which point the true appearance of the devil is revealed in all its ugliness. Sir Bors is offered a choice between serving two beautiful women: one attired in gleaming white, the other in gloomy black. Everywhere else in the Quest, white and black signify in the traditional Western fashion that associates white with purity, goodness, virtue and black with corruption, evil, sin. But here, for a change, the polarity is reversed, no doubt because Bors is already more spiritually advanced on his knightly brethren and it wouldn't be much of a test to ask him to see evil in black, good in white (a test that Lancelot fails at one point, incidentally).
Bors gets it right, thankfully, and the tip-off for us readers that black is virtuous in this case is the echo of the line from Song of Songs where the beloved declares "I am black but comely"; the beloved in this case is routinely allegorized in Christian readings as the Church itself, and the white woman opposed to her in Bors's temptation is the whited sepulchre of the Synagogue. (Friendly reminder: I just report this stuff, I don't endorse it.)
And a few last art notes. This drawing is not the first time I have sketched an image of Cundrie or her French-language equivalent: I first used the description from Chrétien's work to provide the cues for one of the demons I drew for our Lynda Barry-inspired One Hundred Demons sketchbook project (anthologized as Demonstration, though that collection does not include the Cundrie figure). If I can find my old demons sketchbook, I may post that image as a postscript.
Where the sketchbook version was very cartoony, I deliberately sought in this case to make the outlandish description as plausibly human as possible. If the boar's teeth aren't a full span long, we might attribute that to Wolfram's tendency to exaggerate. But I have seen remarkably hairy countenances, including eyebrows that probably could have been braided if their bearers had wished to do so, and I think that this doggy nose is probably in the range of possibility, too.
Finally, I seem to have settled on a potentially very boring pattern for my Arthurian alphabet, what Isaac has aptly described as "the yearbook approach": head shots. In for a penny, in for a pound, though: I think I'll stick with that for the human characters in my mainstream "official" Alphabooks contributions, though I'm still holding out hope for a "second series" of drawings that might include more variety of figure and composition. (We'll see, but no promises—I didn't even manage to get this one done on schedule, and it was a single drawing!)