He lurks in the background of gritty black-and-white photos — a gaunt, too-tall figure with skeletal limbs. Some say he lives in the woods and eats children, a kind of demon descended from eastern European myth. Some say he stalks human prey indiscriminately, wherever he can find it: in basements, outside half-open windows, along lonely streets late at night when only occasional headlights cut across the road. Some say he has no face. Others, that his face looks different to everyone who sees it. But whatever they say, everyone generally agrees on one point: that Slender Man, perhaps the Internet's best and scariest legend, is indeed a legend — an invented character who can be traced back, quite linearly, to an obscure forum where in 2009 users Photoshopped old pictures and improvised a back story for their creations. Tragically — and chillingly — two 12-year-old girls in Wisconsin, seem to have missed all of that. On Saturday, according to news reports, the girls lured a friend into the woods and stabbed her 19 times in some kind of tribute to Slender Man. The girl they stabbed is hospitalized in stable condition. The perpetrators have been charged as adults. "Many people do not believe Slender Man is real," one of the girls said, according to the criminal complaint. "We wanted to prove the skeptics wrong." But as dozens of forum posts, newspaper articles and a handful of academic papers show, there's nothing to prove. Slender Man is a fascinating case study in the creation and codification of Internet myth. And at the end of the day, that's all it is: a myth. • • • In the myth, Slender Man has many origins: Germany's Black Forest. Ancient Egypt. Cave paintings in Brazil purportedly depict his movements. In real life, the story begins in the forums of Something Awful, a humor site for people who enjoy joking about things like Dungeons & Dragons, porn and 3-D printers. But the forums can take trickier turns — they're well-known for tricky Photoshopping and general prankery. On June 8, 2009, a new forum thread invited users to "create paranormal images through Photoshop," which many users did. But the creation of one user, Victor Surge, struck a particular chord: He posted two photos of children haunted by a tall, shadowy figure with tentacles for arms, along with blocks of ominous text: we didn't want to go, we didn't want to kill them, but its persistent silence and outstretched arms horrified and comforted us at the same time . . . 1983, photographer unknown, presumed dead. For weeks, Surge continued posting doctored photos, newspaper clippings and child's drawings of Slender Man, gradually pulling other users into the myth. They contributed their own Photoshops and stories, drawing parallels to older legends and nudging the story along. By mid-June, the thread was solely devoted to developing the mythos of Slender Man, which now — at least according to one authoritative PDF — runs 194 pages long. Because Slender Man was developed collaboratively, by a community of anonymous contributors, that mythos is spotty and varied — much like a more organic urban legend would be. In some stories Slender Man has multiple arms, like tentacles, and in some he has no extra appendages, at all. Sometimes he seems to kill his victims themselves, in vague, mysterious ways that the faux news stories and police reports never seem to specify, before disemboweling them and bagging their organs. Other times, Slender Man somehow compels his victims to kill each other — a particularly grim plot line, given the attack in Wisconsin. In one of the faux news stories, a horse farmer named Ted Henderson shoots his wife in the chest at the Slender Man's behest, only explaining the crime to his psychiatrist at a mental institution three years later. Ted: Ran. . . ran inside. . . got gun. . . Tracy crying. . . Judi screaming. . . r. . .ran to them. . . He had them. . . was holding them. . . Dauton: Who had them? TED: Skinny fella. . . suite. . . Looking at me. . . Judi screaming. . . shoot me. . . SHOOOT ME SHOOT MEEEE! That vagueness — the infinite mutability, the fuzzy details, the ability to adapt Slender Man to just about any time and place — is a large part of what pushed the story off the Something Awful forums and into the Internet mainstream. Slender Man gradually spread onto other niche forums, like 4chan's paranormal board. From there, it would inspire a popular horror Web series called Marble Hornets, several indie video games and an untold trove of sub-memes and fan art, as well as earn prominent pages on Wikipedia and Creepypasta, a site dedicated to Internet horror stories. Creepypasta is the place where the Wisconsin girls first read the story of Slender Man. • • • By 2011, the legend had become so deeply embedded in the Web — and so divorced from its blatantly fictional origins — that even its original creator, Victor Surge, couldn't believe how much it had spread. "I didn't expect it to move beyond the SA forums," he said in an interview with the website Know Your Meme, later adding: "An urban legend requires an audience ignorant of the origin of the legend. On the Internet, anyone is privy to its (Slender Man's) origins as evidenced by the very public Somethingawful thread. But what is funny is that despite this, it still spread. Internet memes are finicky things and by making something at the right place and time it can swell into an 'Internet Urban Legend.' '' That same year, the Minneapolis Star-Tribune reported an entire feature on "the Internet-concocted creature. . . scaring today's teens silly." Only two years had passed since Surge invented Slender Man, and its origins, the Tribune ruled, were already "difficult to pinpoint." That obscurity is, of course, responsible in part for Slender Man's scariness: It appears to eliminate the fourth wall entirely, making Slender Man less a ghost story and more a plausible entity. The further the myth gets from its origins, the easier it is to sift out truth from fiction. The Blair Witch Project used some of the same techniques. And yet the character's appeal goes far deeper than that, says Shira Chess, an assistant professor of mass media arts at the University of Georgia and a scholar of the Slender Man myth. In fact, Chess is unsurprised that people, including teenagers, frequently buy into the Slender Man myth — in short, we're hardwired to believe. "We tell ourselves stories because we (humans) are storytelling animals," she wrote in an email. "And, to that end, horror stories take on a specific significance and importance because they function metaphorically — the horror stories that are the best are often metaphors for other issues that affect our lives on both cultural and personal levels." Slender Man, Chess says, is a metaphor for "helplessness, power differentials, and anonymous forces." He's an infinitely morphable stand-in for things we can neither understand nor control, universal fears that can drive people to great lengths — even, it would appear, very scary, cold-blooded lengths. • • • For whatever reason, Slender Man does seem to have resonated particularly among teenagers; perhaps that's the demographic most susceptible to scary stories, or perhaps they're the people frequenting sites like Creepypasta most often. But the girls in Wisconsin, at least according to statements they made to police, truly believed Slender Man was real: He teleported and read their minds, they claimed. He watched them and threatened to kill their families. "They hoped (their friend) wuld die," the Milwaukee Journal-Sentinel reported, "and they would see Slender and know he existed." But Slender doesn't exist — at least not outside of the YouTube videos, wiki pages and horror forums that have grown up around him. Said Russell Jack, the police chief in Waukesha: "The Internet can be full of dark and wicked things."