I thought I would lend my experiences and understanding of the shadow people to the mythos surrounding these entities.
To me they do fall into several categories and have various effects on people. I also believe they have different purposes.
1. Echo- This is a shadow person that was once alive, once a corporeal being, usually human, though I believe the phenomena can happen to animals as well. The entity no longer has the energy to show themselves as they were so what we end up seeing is a shadow in the form they once held. It is the best they can do. They can be neutral as in they are unaware of us at all. They can be peaceful as in they are not interested in us, mean us no harm and just happen to be hanging out where we are. They can be malignant, meaning they mean us great harm and will do whatever they in their weaken state can to take from us what they lack, life.
2. Watchers- Like the photo, all they are capable of doing is watching, they may not even be aware that they are projecting an image. They do not want anything from us. They just like to watch. I think because it comforts them or reminds them of who or what they used to be. They will fade after a time, they just do not possess the energy to continue for long.
3. Skinny Man- This is an entity reported by many people all over the world. It is a shadow person. It is negative energy trying to occupy space in a positive energy field. The distortion makes the entity appear long and thin. They are always aware and either neutral, unless provoked or malignant and wanting the energy from the living they are infecting.
4. The Man With The Hat- This is an entity that never had human form and never walked the Earth as anything living. It watches to study and when it has enough information on its chosen victim it begins a systematic attack designed to destroy the life-force of their victim. Removing yourself from this entity immediately is recommended and blessing or exorcising the place they are occupying is a must. They will not give up until they are destroyed or they have destroyed.
5. Shadow Creatures – They can assume any form they wish, from a child to a giant spider. If you try to pass through them, it will usually leave you with a feeling as though you sludged through tar and are short of breath. They feed on energy and while not necessarily malevolent they are after the living energy around them, so oops! if they kill you in the process. Avoid and bless or exorcise wherever they have been seen.
6. Wraiths- I put wraiths here because they can have so many forms. They feed not only on energy but on fear and rage. The more they have the less like a shadow they become. Their presence is often noted by a noticeable increase in the tension, fear, anxiety and rage in a room. They find blinding rage to be like ambrosia and will do what they can to cause it. If you find yourself suddenly unable to keep the feelings of rage you felt over your parents not letting you watch tv when your where six, from overcoming you, you might have a wraith sharing your space. Their ultimate goal is to either gather enough energy to cross back through the veil themselves and go after the target of their rage; or to weaken someone around them enough to possess them and then go after the target of their rage. Their only fully formed thought is revenge.
7. Shadowforms- This is an entity created by someone with power. They have been created with a purpose and they will harm anything that stands in the way of their purpose. Once they have completed it, they dissipate. Unless the person who created them is not strong enough to hold their creation, then they must be exorcised or they will keep on harming whomever is handy. They unlike the other forms can take a fully solid form. I know of someone who hit one with their car and the car was severely damaged, they ended up being taken away to the hospital and I am one of few people who believes them that it was a shadowform that was in the road.
8. The Others- Whatever these entities are they were never human and may predate demons. They can for the purposes of watching appear to be only shadow people. However, they most often are seen as children with completely black eyes, no whites. The feeling of malignancy rolls off them, even those with slight sensitivity to the psychic realm, can feel it and are afraid. To anyone with any sort of cultivated ability the hatred of all things human is obvious as well. They will sometimes appear to be lost children, looking harmless and scared. They convince a person to do something that endangers their lives to help them and when the human is past the point of return, they show their true form. They are by far the scariest and malignant of all shadow people.
9. The Screamers – These entities will appear right in front of a person and scream, so that the person only sees red eyes and teeth. A few people are sensitive enough to hear the actual scream, it is said to drive the hearer insane if they do not protect their ears and pray. Whether their intent is malevolent or not is unknown, they may not be aware of the nature of their screams, and just may be suffering unbearable torment. They may be asking for help. Yet there is no way for the living to know.
As with most incorporeal beings, removing yourself from the place they are inhabiting, having the place blessed or exorcised, and removing any object they may be attached to will stop the encounters. Praying at the time of the encounter is very useful, though you must truly believe in whomever you are praying to for it to do any good. If you are a lifelong atheist and you drop and pray when The Shadow Men are after you, keep bending and kiss your butt goodbye. Just a little something to interrupt your sleep and make you think!
Splatters and Screams,