Caverndeep

Caverndeep is one of Orphan’s thirteen splinters. The splinter, which boasts Orphan’s largest oread population, is entirely belowground, a vast system of caves that range in size from claustrophobic to immense—although the word “belowground” implies the existence of a surface. As far as anyone can tell, the only thing beyond Caverndeep’s stone ceiling is more stone.
Much of Caverndeep is under the control of either the city-state Yaocapact or its ancestral enemy Ironmother. The remaining territory is a wilderness of tree-sized, luminescent mushrooms and natural cathedrals of stone, in which all manner of strange creatures lurk. It is a dangerous place for unwary travelers.
The splinter is shot through with rivers and streams, which empty out of hidden channels into subterranean lakes. The Yao venerate this dark water, and build ritual water-wheels to catch its currents. According to Yao lore, all the water in the splinter eventually drains down to the very bottom of the splinter, into a vast, still body of water called the Black Lake. Whether this is literally true is unknown; nobody’s ever descended that far and come back.
Caverndeep is linked by pharos routes to Fel Dhavash, the Orosca Desert, and the Radiant Waste.