Shadow people

Shadow people (also known as shadow men, shadow folk, or shadow beings) are a type of entity characterized by being humanoid, cloaked entirely in shadow, and often disappearing or running away soon after being seen. Most report seeing them out of the corner of their eyes, but some claim to see them directly for a few moments before losing sight.

Varieties
Most shadow people sightings fall under a small set of categories.

Benign
Benign shadow people are categorized as appearing without noticing their witness and do not unnaturally evoke any emotions.

Peepers
Peepers are a kind of shadow person characterized by only appearing within one's peripheral vision while awake, "peeping" around corners. They vanish as soon as they're noticed.

Malign
Much like the benign variety, but their very presence evokes strong feelings of terror. Malign shadow people are occasionally reported to have red eyes.

Hooded
The entity appears to be covered in a hooded robe, and witnesses often report feeling an intense rage emanating from the figure.

The Hat Man
The Hat Man is a shadow person characterized by the appearance of wearing a hat, often a fedora. Occasionally witnesses will report one wearing a business suit or trenchcoat. It is generally associated with ill omens.

Ghosts
Shadow people are not necessarily connected to a ghost haunting, but there are some instances where the resident spirit takes the form of a shadow person. In these cases, they're usually more distinct than the typical sighting and are often accompanied by feelings and sensations unique to them.

Ghosts
Some suggest that all shadow people are ghosts, perhaps stuck in limbo because they never moved on. They're often connected to hauntings, but do appear outside known haunted areas and in one-off instances.

Interdimensional
Others speculate that these are rare glimpses into worlds parallel to or beyond the physical plane.

Aliens
Shadow people and poltergeist activity are common occurrences in the houses of alleged alien abductees, suggesting that there may be a link between the two.

Skepticism
As most sightings take place in the corner of the witness' vision, skeptics are quick to point out that this makes the experiences unreliable and potentially related to phenomena like pareidolia.