After the Great War those races of Darkness, those that were left - those the warriors on the battlefield had represented, slunk away to their home beneath the southern most volcano mountains. There in the deep dark shadows of this range in the midst of the villages stands the Obsidian Castle in the heart of Obsidian Falls. The black glass that is the castle walls rises upward, staggering in stair like fashion as level after level of the castle narrows upward until the final tower rises high above the rest nearly as high as the main volcano itself.
Only the purest obsidian was used in the making of the castle and only the most skilled craftsmen were allowed to work with it. These skilled craftsmen were slaves, of course, as the races of darkness fill their times with ambitious thinking rather than the labors of their thoughts. The village buildings as well are made of this pure obsidian, thus the bleak blackness glitters throughout the region, reflecting the hearts of those whose ancestors were beaten back by the slaves they thought to control for all eternity.
The region throbs with a constant pulse. A constant hum reverberates throughout it. It may be thought maddening to some but this hum is the life source of the Obsidian Falls. It is what keeps the houses of glass from shattering, keeps them warm when they should be cold. Magic is the easy answer for this. However, another answer is just as simple. Long ago the dark races were able to transfer the energy from the underground flow of lava into a primeval generator. This energy pulses through the area, giving strength to the glass walls that rise up out of the ground. Thus keeping them from shattering so easily. Because of this energy a mass can outlast a war within the glass of these walls. Fire can not penetrate, nor can boulders crush. These races of darkness were also able to channel the flow of the lava guiding it in the direction they felt best to serve them. When a volcano erupts, the lava flows safely around Obsidian Falls, beneath the bridges also made of the pure obsidian.
These races of darkness are led by one who has waited for centuries to return to the world and once again take control over those lesser races who would dare, dare think he beneath them. He bides his time waiting for his forces to rise in strength. Oh, they have not simply lain dormant for all this time. No, of course not, but they have not been seen in masses since before the Great War. Now they leave Obsidian Falls in small parties, groups of five to twenty five. These parties raid villages collecting food, supplies, and the needed slaves to carry out their ambitious thoughts. The smaller parties are scouting parties, testing the strengths of those other regions, baiting the people with nightmares and shadows with no explanation.
Credit to: GMineyCricket for description.