What I was angling for was elven gods behind Eluvians appearing in the shape of dragons, as they know primitive humans are in awe of the giant lizard, and it's one of their favored shapeshifting forms, judging by the murals.
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But why remove the autonomy like that?
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I think she's been developing the dwarven history and mythology aspects of her Grand Unified Theory. 
So we assume they were not necessarily dragons in their raw form but could simply adopt dragon form and/or (I tend toward "and" because of Mythal's abilities) remote control dragons.
I see evidence for mind control when considering the Well of Sorrows. My elf girl who drank would say something like "You commanded me here" when Mythal shows up, and Mythals replies along the lines of "Clever girl. I command the voices, and the voices command you." (I don't remember the exact words).
Controlling a dragon must be more difficult than controlling others, how else is the dragon the creature that can stand the taint and the song best? It's mind must be stronger, have some sort of defense mechanism. But, after all, Mythal can command the dragon who will show up at the altar (because I do not think she is that particular dragon herself). And I assume it's safe to think the Forgotten Ones were no less powerful than the elven gods.
(Is madrar still around anyway?)
With what you and electricfish said, we can assume the Forgotten Ones are something different, too, not necessarily dragons. So what we you think they were, magisters/mages/something yet unknown?
Sorry for staying off topic so long. On topic:
