When the turbulent mountains moved, 1000 years ago, they diverted the course of the Anac'ulin underground, so that instead of running over the plains, it carved out its own gorge in the rocky splendour of the mountains. The people of the plain suffered famine and drought and the fertile Anac'ulin valley became the wasteland that is it today, without its seasonal floods to irrigate the land.
But as a result of the diversion of the Anac'ulin, the dwellers of the Mountain Rift prospered, and a plethora of thriving societies developed underground, along the subterranean course of the river, trading by boat with one another and the outside world.
When the mountains last moved, they cast huge boulders to block the caverns where the people of the Rift lived. Although the river still flowed through the underground realm, they were trapped inescapably. Only in far Eo-Sabyad did any shafts of light penetrate the darkness. The people of Eo-Sabyad revered the light, but the other inhabitants of the Rift soon came to shun it.
In the undercitadel of Moezzin, in the great desert cavern of Ckarl, there is a caste system. Since many generatons have passed since the last quake in the Rift, the eyes of some inhabitants have adapted to almost complete darkness. Of course there are still some whose eyes are only able to see in the light, and their eyes are atrophied and shrivelled. The caste-system is between those with shrivelled eyes, and those whose dark pupils capture the few rays of heat from the surroundings and enable them to see in infravision. The "atrophates", as they are called, are inferior, while the "orbates" consider themselves a class apart. Atrophates tend to be more trusting and generally nice people with a good sense of community and helping out. Orbates tend to be arrogant, self-righteous and generally unpleasant people.