A labyrinth of subterranean tunnels and caverns, the Underdark stretches beneath the entirety of Kelbonnar and is home to all manner of creatures that have managed to carve out an existence for themselves there and in many cases, thrive.
For the vast majority of creatures from the surface world who stray down into it, the Underdark is a confusing, winding network of tunnels, caves and caverns, where one can easily lose their bearings and become hopelessly lost. Whilst the Underdark can still be perilous to the humanoids and other creatures who live there, its permanent residents have learned how to distinguish one cave or tunnel from another and how to read signs that appear as little more than bare rock to outsiders. As a geographical entity, the Underdark is as diverse as the surface world in terms of the biomes and regions that can be encountered there. Though large tracts of it are bare, rocky caverns; bioluminescent fungal forests, lava flows, underground rivers and lakes, fields of stalactites and stalagmites, and even entire cities can be found there. The Underdark is roughly divided into three sections, each one deeper beneath the surface of Kelbonnar that the last: The Upper Underdark Thought to be the most labyrinthine of all of the Underdark's levels, the Upper Dark is a mixture of different biomes and habitats and has the most direct access points to the surface world. The Middle Underdark A vast portion of the Middle Underdark is dominated by a large underwater lake, the residual moisture from which makes most of this section feel damp and humid. The Deep Underdark Thought to be on the very limits of habitability for most creatures, the Deep Underdark is a volatile, highly volcanic area.
Fauna & Flora
As with its geography, the species of flora and fauna found in the Underdark are just as varied as on the surface of Kelbonnar. Obviously, most of the flora has had to adapt to a life without light, and fungi, lichens and mosses are the dominant plant species that reside there. However, some plants have adapted to exist to exist on the light emitted by bioluminescent plants, which have whole ecosystems built around them. The picture for the Underdark’s flora is slightly more complex than that of the fauna. Though there are herbivorous species that dwell there, the vast majority are carnivorous and survive by eating other carnivores, or any creature unfortunate enough to stray down into their domain. There are humanoids too that dwell in the Underdark, with the Drow and the Duergar being the most numerous species to be found there.
Connectivity & Relationship to the SurfaceThere are entrances to the Underdark all over the surface world of Kelbonnar, though the vast majority of them tend to be located in mountainous regions, or areas that have experienced a large amount of volcanic or tectonic activity. This means that the boundary between the surface world and the Underdark is incredibly porous, allowing mostly creatures from the deep to emerge at night, usually in search of prey. The existence of tunnels below the surface is not a secret, though as the pervading folktales, collectively referred to as Death’s Endless Passages attest, most humanoids in Kelbonnar know little about the Underdark, other than that it is somewhere to be feared and avoided. Imperial Policy on the Underdark is to keep people as ignorant of the true extent of the Underdark and of the creatures, both sapient and not that live there. Certain surface dwelling species, such as the Vampires of Ymeris are thought to maintain regular contact with Drow and Duergar states and entities that exist below the surface.
Underground / Subterranean