Nilith
Niliths are horrifying sloth-like aberrations who feed on both the negative emotions and flesh of others.12
Appearance
Niliths resemble grey, starved sloth creatures with vicious needle-like teeth, long claws, and piercing red eyes. Niliths are roughly the size of a human, though there is little mistaking these creatures for any humanoid creature.12
Abilities
Niliths have a number of ways to inflict misery on their targets and focus heavily on innate abilities that confuse, despair, and panic their prey. Worse, should the nilith successfully grab some poor creature, the nilith is able to directly implant the target's worst fears into its mind, which often will completely break the will of the target, leaving it defenseless against being eaten.12
Niliths can speak and understand the Common tongue and Aklo, and may communicate via telepathy. They are resilient to mental attacks and against physical force, except that wrought by silver weapons.12
Ecology
Niliths enjoy tormenting sapient creatures with fears and their worst thoughts, especially those who are devout and fair. They often seek to drive their prey into torment, though most niliths are never patient enough to finish this task, eventually getting bored with their quarry's thoughts and fears, killing them, then eating them before moving on to the next prey.12
While native to the Universe, niliths have some strange connection to the Dreamlands, seeming to draw some sort of power from that blighted realm. Niliths are actually remote feeding mechanisms for unknown and more powerful creatures that exist in a distant dimension beyond dreams. This mysterious connection is speculated to be the source of the nilith's long lifespan, that is believed to be thousands of years long.12 So far, any attempt from individuals to investigate how the nilith are bound to these other creatures has resulted in madness before any progress is made.12
Niliths themselves tend to avoid other niliths, which prevents the creatures from becoming overwhelming threats to areas, though a single nilith can still wreak substantial havoc on a community.12
Speculation
In folktales, it is told that if someone has nightmares involving niliths, they are fated to be eaten by one in the future.12