Slenderman

It started with a photograph of the 80s, rescued from the rubble of a fire in a library on the city of Stirling, in California, United States. In that picture you could see a group of fourteen children playing in a local park, but at the bottom and in an attitude of silent observer unnoticed, lays a disturbing and black male figure: high (over two meters), faceless, with black suit, with tentacles, blurred by the shadow of a tree.

The really disturbing thing in the picture was the presence of children playing around the stranger, as if they could not see it. What kid does not attract the attention of a tall, faceless man with tentacles? But the worst came later, as the children and Mary Thomas, the alleged author of the photograph, dissapeared without trace. Their bodies were never found ...

After what happened with that photograph, many others began sending their own testimony about the strange and tall humanoid. Like this, more photos arose of him being in dark forests, solitary and nocturnal urban environments, among  fires, or even inside houses or abandoned buildings. Apparently, Slenderman has been present in the world since the dawn of history, its manifestations vary slightly but retaining its key features.

Finally, based on different evidence and stories, it can be said the following about Slenderman :

His behavior is stealthy, lurking.
He can become invisible, even selectively, choosing who can see him, and who doesn't.
He can distort electronics.
He can modify his figure to some extent: extend his arms, draw his tentacles or to get louder and intimidating.
He has the ability to teleport.
He has mind control and can also induce insanity and mental disorders.
Some sources indicate that Slenderman prefers children as preys.
He likes forests, dark or dimly lit places in abandoned buildings, places with fire or with fog.
He often keeps harassing for years to those who have seen him in childhood, and in many of these cases, he goes years without becoming visible.