Underdark

The Underdark is the vast network of underground caverns and tunnels underneath the surface of The Known World. It is home to a host of evil beings driven deep into the caverns at the time of the The Great Deluge.
The Underdark is a simply mind-bogglingly huge region. Some say that is spans the entire world, just below the surface, and that it has its own civilisations and cities.
In places the Underdark is known to reach more than 10 miles below the surface world, or World Above, as the inhabitants of the tunnels say.
The region has been the primary subject of study for many scholars over the years, and expeditions have been sent down to the tunnels on many occasions. What they have discerned is that the Underdark is not one giant cavern under the world, but rather, many huge networks of caverns and caves. As a result, it is not always possible to travel from one end of the Underdark to the other.
The Underdark is divided into several domains that are similar to continents of the world above. Whilst it is possible to travel from one place to another within a domain, separate domains tend to have very few passages linking them. The major domains of the Underdark have been called the Buried Realms, the Darklands, the Deep Wastes, the Earthroot, the Glimmersea, and the Northdark.
The Underdark's underground landscape varies from small subterranean fissures almost impossible for adventurers to crawl through, to wide expanses of deep water that hide coral caves, hollowed out sections of ice in which creatures live, and places where fungus, bones, or even pure force formed "caves".
This varied landscape is as dynamic as that of the surface world. Some areas are always changing over time because of underground magma rivers or the emptying of underground lakes due to cracks in the rock formed by earthquakes. This means that the few maps of the Underdark are highly unreliable.
The Underdark is extremely dangerous, especially to those not native to it. There are the usual dangers associated with caverns: claustrophobia, occasional poor air circulation, oppressive silence, and getting lost. There is no light except for occasional patches of fluorescent fungi; most Underdark inhabitants either have highly developed senses other than sight or have developed darkvision. Food can be extremely difficult to find, and much of the natural vegetation is reportedly poisonous.
In addition to those dangers, the Underdark is also the home of many predators and often-hostile races. The Drow retreated here after the The Great Schism, building a new home beneath the surface of the world.
There are many entrances to the Underdark. Some of the known ones are beneath the dwarven city of Koldor's Hold, within the town of Drakenham, and deep within the Waleen Peaks.

Exploring the Underdark by Unknown

Type

Underground / Subterranean

Location under

The Known World