The way I had it outlined in my history, the predecessors of the Lumen specifically settled around the lakes, ignoring all of the steppes that they'd conquered. Homestead and Silver Port, the two biggest cities, are both either along a river/lake or right next to one. The east, further away from the lakes, is where I had Lumenor's human minority set up, the descendants of the clans that originally inhabit the place. I figured that since the area is flanked by lakes and rivers and is on the south-western edge of the 'Steppe' region, it'd be capable of housing cities dependent on agriculture.

...And all that's assuming that Lumenor is agriculturally self-sufficient. The river-way connects directly to the coast and the Eastern Delta. It's feasible that a portion of the food in Lumenor is imported.