Slenderman is a notable legendary figure for two main reasons. He's the world's first mythical creature spawned on the Internet, and there's no question as to whether or not he really exists. Slenderman was created by Floridian Eric Knudsen in 2009 on the Something Awful web forum, where people doctor photos and then write stories about them. Knudsen's photo depicted a tall, willowy, fuzzy figure. He didn't initially write much about it, but hinted at its evil character.
Fellow forum posters added details, as did Knudsen. Over time Slenderman spread onto other forums and his description began to morph. Sometimes he had multiple arms, other times none. Sometimes he killed his victims, other times his followers killed people for him. Often, you never knew what happened when he caught someone – just that it likely wasn't pretty. Although Knudsen eventually stopped developing the Slenderman character, it lives on through the Internet and its fans, many of whom are teenagers. Tragically, in 2014 two 12-year-old girls almost killed a friend by stabbing her 19 times, in the hopes of pleasing Slenderman, who they thought was real [sources: Biggs, Dewey]. That's the most terrifying Slenderman story of all.