I realized that mountains typically form deserts and lush areas via the rain shadow effect(in other words, most of the rain is on 1 side of the mountain forming a lush area and barely any rain gets to the other side, forming a desert).
So would the mountains in this region form a desert and thus not a good place for civilization(I mean, being underground mitigates the heat but still, the sand could be disastrous, especially for babies) or would the swampland that the Black Sword River leads to just 100 miles south be enough to not form a desert?
Area with mountains in question
Area 100 miles north of civilization with tributaries of the river
Area 100 miles south of civilization that is all swamp that the river leads to.