Wait I just had a thought if he dided while the dunmer where chimer why does he have dark skin?
The fact that he's been living in a volcano for thousands of years probably helps.
Also, I've read many culture's mythologies, and I've never read anything about Marduk having four ears. Where'd you get that from?
For the record, I actually don't think that Dagoth Ur mesh is actually what he looks like. My theory is that the devs just took an Ash Vampire mesh, modelled on a mask, and just went from there. The reason he looks like an Ash Vampire under there is because that
is an Ash Vampire. I'd say that under that mask he looks much more like an Ascended Sleeper, or other high-ranking Ash creature, and that his face has already sloughed off a long time ago and now it's a writhing mass of tentacles. Be GLAD he has that mask on.
EDIT: Okay, I've came up with a good description of my view on Dagoth Ur under the mask. Spoilered because there'll definitely be some folks that'll think it's icky. NOT FOR THE SQUEAMISH OR THOSE EATING LUNCH, you have been warned!
Spoiler Without his mask, Dagoth Ur's face is horribly wasted away beyond recognition as the pinnacle of an Ash creature. The skin of his face from his scalp to the bottom of his throat, and extending back to behind his cheekbones, has melted away, leaving only bare skull and still-beating veins. His Coprus-ridden skull is sickly pale and distorted with many bulges, grown bulbous from the years of living within Red Mountain. His eyes, red and swollen due to the irritation of the surrounding volcanic ash, are all corrupted, and the third eye in the centre of his forehead watches on in their place. One eye has sunken back into its swollen socket, while the other has totally disintegrated. From various growths on his skull come great ashen tentacles, writhing chaotically around what is left of his face. From his torn scalp comes his mottled, ragged hair, grown rough from Coprus and ash. As he speaks, the tentacles surrounding his mouth part as his boil-ridden tongue moves about his rotten, crooked teeth, and as his third eye stares down, you know he means buisness....
Man, If only I had a scanner, I would SO draw that for you.