The Upper Growing

Underneath the surface of the valley surrounding Irrum Vath are a network of waterways that have carved their own passages into the earth. In some places, particularly around the hills known as "The Scars", there are cenotes and ravines where this network is exposed to the surface. The water level of these caves fluctuates with seasonal surges of snowmelt, and all water that enters inevitably flows towards Irrum Vath. The closer one follows these caves to the mountain, the more the shape of the caverns seems to be no longer defined by the flow of water, as if the stone itself was immune to inexorable erosion. Eventually, the water reaches the main complex of caves directly beneath Irrum Vath. These passages are all but inaccessible most times of the year, and it is recommended one enter the caves through the gates around the mountain rather than drowning in these waterways.
All of these passages drain water into a region of the caverns under Irrum Vath known as "The Upper Growing". The exact boundaries of this region is poorly defined, but generally accepted to mean anywhere located between the yet-unflooded districts of the subterranean urban ruins near the surface and the dry caves the water does not reach below. Below the dry caves is "The Lower Growing", where water is drawn from unknown places beneath the earth rather than funneled from the surface.
The region is named, as one might suspect, for the massive variety of native flora and fauna. Massive glowing mushrooms and luminous trees dominate the largest caverns, bright enough to support photosynthetic plants in absence of sun. In these places, pine trees and ferns resembling those on the surface intermix with a staggering variety of fungi and stranger things besides. In the reservoirs of cold clear water there are fish, crustaceans, and aquatic insects all living among sprawling reefs of freshwater coral. The entire region is a wild tangle of living things spilling over onto each other, and cataloguing it all is an (unfinished!) task that has consumed the Irra for many long years.
Traditionally, the region is home to many of the Irra enclaves that can not be found about the upper spire of the mountain. Kobolds live here too, though less so in recent times. The mineral riches of Irrum Vath are not so great here, and communities here are also first in line to be endangered by newly feral monsters rising up from the deep. The largest Kobold communities live in the border regions above and besides these caves, where the mining is for now more lucrative but water is not so far as to be scarce. Consequently, many Kobold power struggles have manifested as conflicts fought across the Upper Growing by these neighboring clans attempting to project power. Notably, the clans that are more isolated from the Upper Growing are utterly dependent on the artificial lights of the Lymantria for the growing of crops. Some industrious Kobolds continue to experiment with cultivating the keystone species that provide the luminescence necessary for the growth of their crops. The Gates Below are also found here, in line the with the main spire of Irrum Vath as it extends down into the earth. The community around the gates is one of the largest in the region, and represents a major stopping point of any seeking to venture deeper into the depths. The Bajir outlanders recently established an outpost here as well, though only time will tell if it lasts.