aka “the Underdark”
The region most widely known as the Underdark is an entire world beneath the feet of the surface dwellers of Nordock. It is a vast, choatic series of interconnecting tunnels and caverns driving ever deeper into the heart of the world itself. Inhabited by monstrous and evil creatures that shun the daylight, the Underdark teems with entire cities and nations of Deep Gnomes, Drow, and Duergar. It is also home to even stranger races as well as slaves of just about any intelligent humanoid found on the surface.
These evil beings battle or trade with each other for resources, magic, and power, forming alliances that collapse when plots unravel or better opportunities come along. As complex as the civilisation above the crust of the world is, the world beneath the world is just as filled with history and intrigue.
The Underdark is a harsh realm where two overwhelming drives rule: survival and the destruction of your enemies. Perpetually dark in most regions, the Underdark is filled with creatures that long ago developed darkvision or enhanced senses to compensate, often becoming intolerant of true light as a result of their adaptation. Some places are dimly lit by glowing rocks, luminous crystals, or phosphorescent moss, lichen, and fungi. Bizarre plants are common, and visitors usually find it impossible to identify which are hostile or poisonous without magic or potentially lethal experimentation. The most precious resource is fresh water, since the Underdark has no rain and inhabitants must rely on whatever filters down from the surface. Those who discover water hoard it and protect it with their lives.
Because of the scarcity of certain resources, each city often specializes in producing a few items and trading these with neighbors in peaceful times. A typical trade caravan consists of several dozen heavily armed merchants and soldiers, with two to three patrols sent forward or behind while traveling. Although the tunnels are generally silent, echoes travel far, and a skilled Underdark scout learns to recognize subtle signs of natural animals and lurking threats by their echoes alone. Wealthier cities teleport caravans to their destinations or use existing portals to speed travel, and access to a convenient portal is often the cause of lengthy wars between nearby cities. Cities that develop a reputation for killing or enslaving caravans in peacetime (as opposed to exhibiting cool hostility and rudeness, which are expected) usually find themselves cut off from valuable resources and made easy prey for aggressors.