Upperdark
The Upperdark extends from the surface to a depth of about 3 miles. Varied races inhabit this region, including chitines, drow, dwarves, giants, all manner of goblinoids, orcs, svirfneblin, and wererats. Scouts from deeper races often venture into the Upperdark in order to trade with (or prey on) the races native to this area. The Upperdark’s main import from the surface is slaves. Slavers from evil-aligned cities in the Upperdark make frequent forays into the light to capture new slaves for use as either labor or food. They also trade for textiles, grains, fruit, and weapons. Their exports include raw ore, refined metals, gems, and native Underdark plants.
Travel in the Upperdark is relatively easy. Multiple paths to a single point usually exist, thanks to millennia of natural processes, volcanic activity, burrowing creatures, and various races cutting trails through the rock. In most places the surrounding earth is composed of rock, but near the surface, tunnels can be hewn out of tightly packed dirt, allowing creatures with burrow speeds that can’t cut through rock to blaze their own trails in a pinch.
Surviving in the Upperdark
Survival checks made to hunt, forage, and avoid natural hazards in the Upperdark use the same DCs as normal surface conditions. Basic amenities such as light, air, food, and water are less available in the Upperdark than on the surface, but they are common enough.
Luminescent flora and faerzress provide occasional light, though not consistently enough to allow a creature without darkvision to travel without an independent light source. Vents from the surface keep air fresh and moving in the passages, so air quality is rarely an issue. Enormous underground lakes spread across hundreds of miles in some regions, and water trickles down from the surface in many others. Many water sources are guarded or fouled, but quite a few are both clean and open for anyone to use. Many different types of wild fungi are edible, and the Underdark equivalent of small game (rats, dire rats, lizards, and giant vermin) can easily be found in the tunnels. Domesticated animals, such as deep rothé, can also be found near most major population centers.
Denizens of the Upperdark
Most Upperdark inhabitants traffic with the surface world in some way, either trading with or raiding their upstairs neighbors for things they can’t get in their native habitat. They also trade with (and raid) each other. No Underdark community is ever really friendly with another, but Upperdark settlements often observe wary truces with their neighbors.