Slender Man

The Slender Man (See other names to the right) is a creature or being with various nebulously defined characteristics and abilities. Slender Man was first mentioned in Something Awful Forum's "Create Paranormal Images". Slender Man generally appears (in modern times) as a tall man in a black or grey suit, red or black tie, and white shirt, with no eyes, mouth, or clearly defined facial features. It has no hair, and generally has normal-looking bare hands. Slenderman typically is depicted in imagery and literature as between 6 and 15 feet tall, depending on the situation, and in video as around 6-7 feet tall. Because of its inexact nature, and differences between series, no one has yet determined what it is. Currently, the two leading theories as to what the Slenderman may be are the Tulpa Effect and Quantum Theory. The internet popularity of Slenderman has spawned a massive amount of interconnected ARGs, collectively known as the Slenderman Mythos.

Basic Description:
In almost every description Slenderman's basic attributes will vary greatly, however several basic traits are typical of his behavior. He is shown to behave in a very passive aggressive manner, stalking targets for years at a time, torturing his target mentally for various unknown reasons. He is rarely ever shown in a benevolent light and is typically shown as a malevolent force. This behavioral pattern has an uncertain reasoning behind it, and exactly why he behaves in such a way has yet to be fully ascertained.
The most important factor about Slenderman is the mystery. He lives unlike any human being despite having a similar appearance to one. It is uncertain if he is social, or even understands human languages or behaviors, nor why it is humans appear to be his main target. His targets will typically behave in off ways as if possessed (Proxy), but whether their psychosis is causing them to speak for him or for themselves isn't entirely certain either.
Slenderman's appearance is variable as the years go on, but as of to date the most recent appearance is that of an abnormally tall human with long arms and no face whom is wearing a business suit. Again it is uncertain if his suit is real cloth or some form of skin molded into such an appearance. If it is the former, this would imply an intelligent being attempting to try to blend in. If it is the latter, it shows a being whom is extremely adaptive and evolves to match his environment and stick out less (or more).
Slenderman's appearance provokes a wide range of responses, the most common being fear. This is partially due to his extremely towering size over a full grown adult, which mimics the childhood fear of adult humans bigger than the child. His behavior also factors into it. Finally, the main fact is he is completely unable to be described in human terms. While a description in words can be given, human language lacks the ability to truly define the entity until such a time as when humans can interact with him (if at all possible). This problem stems from the fact that he operates in a plane of existence further from humans. This is believed to be fourth dimensional space which gives him powers a human cannot understand due to humans living in three dimensions of space and being unable to comprehend the fourth dimension at this time.
In total two major types of Slender Man descriptions exist. The original versions depict him as not only malevolent, but extremely dangerous. He will do odd things such as removing organs and placing them in bags, impaling targets on trees, and aggressively stalking targets after a period of time. A contemporary depiction shows Slender Man as being extremely passive aggressive, often letting a person slowly delve into madness at their situation until being unable to cope. If invited to anger, he will typically charge a target down until caught and vanish with them to unknown locations. This version also shows an odd response to electronic equipment and causes massive problems with audio, surveillance, camera, and other various electronic devices with displays or audio. Sometimes an individual can determine if he is near simply by how certain electronics react such as radios, televisions, or cameras. How powerful this effect is seems to vary, and can either be due to Slender Man's own state of aggression, or other outside factors either inside or beyond Slender Man's control.

Abilities:
Slenderman's original abilities included invisibility to select people, adult humans, or anyone without use of a camera, the ability to change height and body shape, the ability to shape its arms into tentacles, and the ability to sprout tentacle-like appendages from its back and shoulders to be used as additional arms or legs (or simply to instil fear into its prey). Many stories seem to indicate that it can control a person's mind, which became the basis for the Proxies in the video ARGs, a trend that would later spread to Slenderblogs. Slender Man also had connections to children, with many of the original stories revolving around disappearing children or featured Slender Man being sighted in photos with children.
As more stories came forth, however, the use of tentacles and tentacle-like appendages became less common, and the invisibility was limited or eliminated depending on the storyteller.
EMH, TT, ML, and DH all contain some sort of video and/or audio distortion, indicating that Slenderman has some sort of effect on modern digital instruments. This does not appear in any of the original accounts- however these mostly make use of photographs and video of primarily lower-tech varieties. EMH Has applied this distortion to be the effect of "Sigma Radiation", a radiation given off by Slender Man and The Rake. Sigma Radiation is also contagious, as it entered Evan's blood-stream when his arm is brutally maimed by The Rake
EMH and ML also make use of "Slenderwalking", a term created to describe Slenderman's apparent teleportation, appearing, and disappearing at will. EMH independently indicates the use of selective invisibility to groups or individuals through head tilting, and also spacetime warping/teleportation between locations. Similar abilities were seen in early Slenderman accounts. EMH also hints at the affecting of mental health or control of it.

Association:
Slenderman makes association with several groups, individuals, or creatures.
The least known of these is the unknown organization tracking, observing, or involved with Slenderman, whose identity or name is yet to be confirmed. The Organization appears only in early Slenderman written accounts, and makes an (assumed) appearance in only one ARG, DarkHarvest00.
The SCP Foundation, though mostly unrelated, maintains hold of a creature known as SCP-582, aka "Bundle", whose appearance and nature is similar to Slenderman. It is possible that Bundle is a local dialect or local version of Slenderman. SCP is unable to currently permanently contain Bundle, indicating that because it is not stationary, it could be the same entity as Slenderman, or at the very least Bundle could be acting out a story and thus recognized as Slender Man. It is to note, however, that said entity is also very different from Slenderman. See the article SCP-582, aka "Bundle"
Slenderman has links to many Proxies, or insane individuals under its control or influence. The nature of Proxies, their workings, etc, are yet unknown, however Proxies make appearances in MH as Masky/totheark, EMH as HABIT, and TT as Observer. Slender Man has also spawned many philosophical and theoretical cults made up of uninfluenced but aware individuals, such as in Darkharvest00.
The Rake is the name given to another mystery creature that is somehow linked or associated with Slenderman. The Rake has a far shorter history, and only real appearance of association with Slenderman or a Proxy is through the video accounts of EMH.