Underdark in DnD 5e

Go where the sun don’t shine

Geography

Layers of the Underdark

The Underdark is spread across multiple depths which themselves typify a different atmosphere and ecosystem:

World above

The name given to the surface of Abeir-Toril above the Underdark, where the sun is able to shine upon the land.

Upperdark

The region 0-3 miles below the surface. It is here that surface and Underdark dwellers will typically meet. The Upperdark is generally less hostile than other parts of the Underdark though this area can often operate as a last defence between the surface dwellers and the inhabitants of the Underdark; particularly from the warmongering drow.

Middledark

Located 3-10 miles below the surface, this is where most of the Underdark civilisations exist including those of the drow, duergar and svirfneblin.

Lowerdark

Any portion of the Underdark below 10 miles is known as the Lowerdark, a place where even experienced dwellers of the Underdark are afraid to go.

Topography

Rather than being a single, giant cavern, the Underdark is split into multiple large caverns and caves. In many instances, these interconnect, but in others, they remain separate from one another with no discernible passages between each area. These distinct areas are known as domains, the main ones being:

• Buried Realms
• Darklands
• Deep Wastes
• Earthroot
• Glimmersea
• Great Bhaerynden
• Northdark
• Old Shanatar

The landscape is typically made up of caverns, tunnels and fissures of hugely varying sizes with rocky features filling the caverns and a variety of pools, rivers and even inlets from the sea and magma rivers found within the areas of the Underdark. Earthquakes, magma and changing water features often mean that mapping the Underdark is unreliable as the landscape is subject to change.

Traversing the Underdark is typically a perilous endeavour without much training and protection The only natural source of light comes from luminescent fungi and the occassional, luminous rock. Without sun or rain, large portions of the Underdark lack a source of natural food though rivers and fissures can at least provide water and subterranean plant-life does grow there (often fungal or mossy in nature). The caverns are often silent, with stale or even poisonous air emitted from fissures and volcanic activity.

Inhabitants of the Underdark

The Underdark is inhabited by a surprising variety of creatures for such a dangerous and hostile environment. Civilisations of drow, duergar and svirfneblin have made the Underdark their permanent home. Alongside them are the monsters and even cattle that inhabit the Underdark finding more natural dwelling places.

Underdark creatures

Due to the nature of the Underdark’s dank caves and deadly inhabitants, creatures that dwell here are different from most surface dwellers. Creatures and plant life have adapted to having no sunlight meaning fungal vegetation tends to thrive above other forms of plant life. This has even given rise to a large myconid population (fungal bipeds).

many creatures have adapted to have darker skin and to be able to see more clearly in the dark. This is typified by races like the drow, duergar and svirfneblin who are variants of elves, dwarves and gnomes that live deep in the Underdark.

Though many creatures can find themselves within the depths of the Underdark, the following are creatures native to the Underdark including:

Aberrations

• Aboleth
• Beholder kin
• Chuul
• Cloaker
• Dereo
• Flumph
• Grell
• Mind flayer
• Otyugh

Beasts

• Giant spider

Demon

• Draegloth

Giants

• Fomorian

Humanoids

• Deep Gnome
• Drow
• Duergar
• Grimlock
• Kuo toa
• Quaggoth

Monstrosities

• Carrion crawler
• Darkmantle
• Hook horror
• Mimic
• Piercer
• Purple worm
• Roper
• Umber hulk

Oozes

All varieties of oozes enjoy the dank darkness of the Underdark.

Plants

• Gas spore
• Myconid
• Shrieker

Undead

• Ghast
• Ghoul

Underdark civilisations

The drow in particular seek to subvert and enslave, dominate or destroy all races of the Underdark (as well as to destroy their mortal enemies; the surface dwelling elves). They build city states ruled by an oppressive council of Matron Mothers that keep other drow in line through threat of torture and death for disobedience. The cities of the drow are extremely hostile and welcome few outsiders unless as slaves or for trade. Even then, most races are treated as below the worth of any drow.

The drow cities are beautiful, if dark and foreboding structures that merge with the natural stonework of the caverns they’re built. Despite their beauty, there is a sort of chaos to their creation with little organisation to how cities are built, with family houses working autonomously to create buildings for their own house. Usually, buildings by the family houses were a demonstration of wealth and power meaning a vast disparity in the quality of architecture. Beyond this, were the houseless drow and slaves that dwell in much poorer housing, often made of clay or other weakened material.

The most well known city state is probably Menzoberranzan, the city of spiders and birthplace of Drizzt Do’Urden as well as the setting of portions of the Dark Elf Trilogy by R A Salvatore.

The city of Ust Natha is featured in the video game Baldur’s Gate II: Shadows of Amn in which the protagonist finds themselves attempting to leave the Underdark by infiltrating the city. Of course, equally great dangers await outside of Ust Natha including settlements of mind flayers, beholders, sahuagin and svirfneblin.

Other known drow cities include: