Underdark

The Underdark is an underground area in the world of Exandria on Critical Role, similar to the Underdark featured in many other RPG campaigns. A dark and hostile place, the Underdark is almost a world unto itself, with civilizations, monsters, politics, economies, and threats that are mostly separate from the surface world.

Environment
As a subterranean environment, the terrain of the Underdark is composed primarily of earth, stone, water (both still and running), and magma. Passages navigable by humanoids range from narrow tunnels to expansive caverns. Without sunlight, the Underdark exists in a perpetual night with the exception of the light from such sources as bioluminescence, enchanted hotstones, fire, and magma.

Moisture in many locations will condense on the walls and ceiling, and when it drips from the ceiling, the water droplets carry minerals and earth, which deposit on the dripping points from the ceiling and the landing points of the floor. Over time, these deposits form what are known as stalactites (hanging deposits, often shaped like downward-pointing spikes) and stalagmites (resting deposits, often shaped like spikes or conical mounds). From a combat perspective, stalactites may be broken free and allowed to fall as spikes, while stalagmites may offer cover or hiding spots if large enough. Both mineral formations may also hide dangerous denizens of the Underdark, ready to ambush unsuspecting creatures.

The Underdark may feature a wide variety of fungal growths and even mushroom forests.

Creatures
Most Underdark creatures either are blind (with no eyes or with vestigial eyes) or have excellent darkvision and/or infravision. Many creatures have other highly developed senses to compensate for the lack of sight, such as tremorsense or a keen sense of smell and/or hearing. During Vox Machina's travels in the Underdark, a series of rumbling noises kept occurring, and an illithid named Clarota advised them to keep still so as to avoid attracting unwanted attention through tremorsense.

Many different—usually hostile—creatures live in the Underdark:
 * Aboleths
 * Basilisks
 * Bulettes
 * Cloakers
 * Duergar (gray dwarves)
 * See also:  Category:Duergar.
 * Fomorians
 * Goblins
 * See also:  Category:Goblins.
 * Gricks
 * Kobolds
 * Illithid
 * Intellect devourers
 * Ogres
 * Ropers
 * Svirfneblin (deep gnomes)
 * Trolls
 * Umber hulks