"What do the Huergar eat?"
A simple enough question, but one with very large implications. The Huergar do not seem to have any sort of large above-ground agriculture, despite having a high population living underground. In fact, their buildings can only be seen in very small pockets of the continent, with the majority of the society being located entirely below the surface.
No above-ground farms, no above-ground ranches, nothing living above ground aside from some Minotaur guards. Many people haven't even heard from them in some time, to the point that one Tindremene wondered if they weren't all dead in some old Huergar ruins that ended up being inhabited by at least one Huergar, Kanniku, who was answering to the council.
So if the Huergar have a significant underground population, what feeds them? Some time ago I proposed Large Underground Areas (among other things) on a whim, but now that I think about it more... is it possible that I was right on track? They must have enough resources below the surface to sustain their populations if they can remain isolated for so long. There's no sign of trade going on, and the only interactions we know of are the Huergar and Khurites occasionally interacting with each, which isn't enough to support an underground society with a significant population.
Considering that we can delve below the surface and find many things living under the surface, from giant spiders to huge mushrooms and plants -- it's entirely possible that the fauna and flora of Nave are rich enough in a subterranean environment to sustain a population. Furthermore, this could be an explanation as to how they, and indeed all underground societies such as the Sheevra get their breathable air.
It is no surprise to me that the Huergar are able to sustain themselves so completely. Their technology is impressive, they seem to have harnessed lava and are able to use it at their whim, there's probably a lot more to them that we have yet to discover. For all we know they have underground farms and more cities than we know of. Even in areas without much oxygen, I can't imagine the concept of ventilation would be hard for them to grasp.