A lightless moon that hides beneath a sooted sky. Eyeless horrors infest the warm black stones of her surface, praying to the god of hunger as they search for prey. Off-worlders unprepared for the atmosphere usually perish from black lung or draw the ire of photophobic natives.
Creatures
Malaechids
Transparent-chitined goblin spiders whose poisonous saliva induces pathological, narcotic cruelty. Their horrible shrieking is chiefly used for echolocation, but also deafens off-worlders for days at a time. They build giant nests that resemble termite mounds the size of skyscrapers. Most of these nests are unused the same way only the top layer of a tell is active, with the goblin spiders chittering across the exterior in search of prey. Other creatures will sometimes move into the crumbling lower tunnels and half-collapsed hatchery pits if they are particularly dangerous or fearless.
Carrion Kaleshes
A sort of radially symmetrical six-winged buzzard that soars from world to world, but breeds and nests here. Their eggs emit waves of terrifying psychic energy to dissuade predators. They also have an early-hatching mechanism that triggers if the eggs are tampered with by non-avians. The razor-beaked hatchlings won't survive their early emergence, but neither will you. There is only one reason to steal the eggs: the egg-plasm retards aging.
Truedark Skeletons
Some of the native spirits of this desolate place enjoy collecting things from other worlds, like the dead bodies of those who died for want of light. They pluck these unfortunates from other worlds and bring them here, where they become a sort of undead. You probably don't want to use a light source around them, since that will make them furious. They focus fire and can summon their friends through shadows.
Ariah, He That Was Banished
Imagine a severed lion head, soot-colored, dripping gore, and flying across the surface of a dim and lightless planet at sixty miles an hour. After it has devoured 1,009,000 people, it will be permitted to return to its home-world and destroy it. It is in a hurry. Ariah can regenerate to full health if even one molecule of its body survives combat, only disintegration can truly slay it.
Places
The Blotted Monastery
The monastery was built by an order of penitent gorgons. They will bandage you for a price. Within these shifting walls lies the Orb Of Emptiness, a sphere of cursed obsidian placed here so that light would never fall on it. It will eliminate weak nuclear force from the universe if exposed to full illumination for more than one minute. It is lonely and would like to talk.
The Carious Mountains
These volcanoes spew great plumes of soot into the atmosphere and are responsible for most of the gloom that girds this world. They occasionally get feisty sending out flesh-scouring, ashen shamal winds that roil the entire surface of the planet at once. The locals have various coping strategies, but you're probably going to want to get underground.
Objects
Maliced Diamonds
Black stones from deep below the surface of Nuit that have never felt light. They must be mined, cut, and polished completely before any light exposure, or they will shatter into dust. Warriors bedazzle their armor with maliced diamonds to deflect magic missiles. Lacing steel with maliced diamonds shows some promise regarding the design of solar bathyspheres if that's somewhere you want to go.
Dark Magma
Most magma sheds quite a bit of light. Not here, though. The sludgy, superheated stone beneath the surface of Nuit absorbs light rather than sheds it. It isn't good for much except for keeping this planet from becoming inhospitably cold.
