The Tenuis Daemonium is a humanoid pseudo-demon which enters this plane at the command of its creator. Physically they are exceedingly tall, approximately 6 to 7 feet tall, with very long arms, hands, and fingers. They often appears to not have faces, though this is not entirely true, they do have facial features but these features are often hidden and only come out when the creature needs to use them. They are technically sightless in that they do not see slight, they see energy and aura and this is how they identify people and navigate the world. The creatures are incredibly strong able to life 10-15 times their body weight without issue. They are intelligent and able to use complex tools with human level intelligence or higher, depending on how much their creator has imbued them with.
Generally the creatures have no name and do not speak, they they are capable of speaking. When they do speak a strong sense of fear permeates into those who can hear the voice. The voice itself sounds like a cacophony of screams coming together to form words. The experience has been noted to be at the very least "deeply unsettling" and at the most "nightmare inducing" and "traumatic". Records indicate cases of people being driven insane by continued attempts to speak to one of these creatures.
Memetic Capabilities
It has also been noted that the creatures have some kind of memetic abilities. Instances have been reported that the creatures are able to alter the perception and memory of nearby people. Usually this is used as a way to stay hidden, a sense of foreboding and a desire to turn back is most often reported. Also reported are instances where people forget what they were doing and then spontaneously leave. It is not known if other memetic abilities exist.
Creation
The Tenuis Damonium is created by a greater demonic force either as some kind of foot-soldier or proxy operator within an area of the material plane. Most often when the particular demonic force cannot enter the plane itself. Holding one foot on each side of the line their energy inside is held together and anchored to the prime material plane by their body. This body is sustained by their continued absorption of supernatural energies. The number of these creatures which can be created is directly tied to the amount of power a demonic entity is able to bring into the plane, usually the energy needs to be anchored by something in the plane. The most effective anchor are Demonic Runes written in blood or some other potent physical embodiment of Aether.
Purpose
Such a creature has one purpose and that is to serve the entity which created them. They are in a constant kind of contact with the creating entity as it sustains their life force. They do as the entity wishes them to do. Often times this is to guard some location of value or perform tasks which the entity cannot perform themselves on the plain they are in.
Cultural References
These creatures have been seen in many different areas of life. It is believed they are the inspiration of the phenomena known online as "Slender Man" during the 21st century. Also probable that some variation of these creatures could be responsible for sightings of "Grey" type aliens during the 20th and 21st centuries. Earlier reports attribute these excessively tall figures of mythos common to many cultures across Earth. It is also likely that television shows depicted such creatures in various forms, though whether or not this is from the pop culture phenomena or actual sightings is impossible to say, a notable resemblance of this is within the Doctor Who villain of The Silence a major plot point in the early 21st century for the television show.