Demon Valley is a ravine extending for twelve kilometers, where the flat wilderness sinks, forming a long narrow valley. Many of the buildings on either side are built into the mountain or directly excavated into caves. Fences were installed outside these caves to house slaves.
However, now the fences are all removed, and all the slaves have been freed, because the three leaders of the Demon Valley are dead, and a once-in-a-millennium Sword Saint has emerged from the human Ice City.
The environment in the Demon Valley is actually the most advantageous, because at the end of the ravine is the Great Rift, a chasm so vast it nearly splits the plane in half. This leads to a bursting hot lava, forming a ceaseless Lava River.
The chasm blocks the Resting Wind, making it spring all year round in Demon Valley, without distinctions of the seasons. Thus crops can be grown twice a season.