Most of what Mown said is largely what I've been thinking. Exception/elaboration:
I have considered 'Frostblight' to be the part of Frostwynd that is furthest from inhabitable (like 'the great white north', 'above the tundra line', 'above the arctic circle', etc). I expect that on each side of the Maraka divider zone, the areas close to Maraka are not nearly as lifeless and bleak as the parts further from it. I see 'Frostblight' as a synonym for 'the bleakest reaches of Frostwynd'. And we should probably have a similar uber-Illpyre region as well. Which might well be where the Viashino and elementals live - an area too hot for human life.
This all might just be the Canadian in me, where ~80% of the population lives in the ~10% stripe of land closest to the southern border, land that was settled because it was a lot more arable than the colder northerly reaches.
Basically, this is my Starstill:
Red is Illpyre. Blue is Frostwynd. White is Maraka. Parts of Illpyre and Frostwynd close to Maraka are where the humans live, where the cities are built. The 'polar' regions are too cold/hot for human/plant life and that's where only species especially adapted to those extremes might 'live'. In Frostwynd, that would laregly be the mechanical, in Illpyre, that's largely heat-adapted animals and pyro-based 'life'forms.
The 'sun' is directly above Illpyre. The sun only shines on Illpyre. A moon on the opposite side (of Frostwynd) reflects just enough light that Frostwynd isn't bathed in darkness, but a low, nonwarming glow.