The Slender Man (also known as Slenderman) is a fictional supernatural character that originated as an Internet meme created by Something Awful forums user Eric Knudsen (a.k.a. "Victor Surge") in 2009. It is depicted as resembling a thin, unnaturally tall man with a blank and usually featureless face, wearing a black suit.
Slender Man first appeared in Something's Watching. In the beginning, he was seen kidnapping a young, innocent child and presumably turning him to another one of his Proxies.