Slender Man, aka The Slender Man, Slenderman, Slendy, Der Ritter, or Der Großmann, is a creature or being with various but not clearly defined characteristics, abilities, and links. Slenderman was first mentioned in Something Awful Forum's "Create Paranormal Images" thread, along with two photos of Slenderman. Slenderman generally appears as a tall man in a black or grey suit, 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 depited in imagery and literature as between 6 and 15 feet tall, depending on the situation, and in video as around 6-7 feet tall.
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 warp and shape its arms into tentcles, and the ability to sprout tentacle-like appendages from its back to be used as additional arms or legs.
As more stories came forth, however, the use of tentacles and tentacle-like appendages became less common, and the invisibilty was limited or eliminated depending on the storyteller. Slenderman also had connections to strange fires and children- many of the original stories revolved around disapearing children, or it being sighted in photos with groups of children.