Slenderman is perhaps the best-known meme to come out of "creepypasta," the short horror stories that spread anonymously across the web. Originally appearing on Something Awful in 2009, the mysterious and faceless creature has since inspired a large and loosely defined mythos, endless new images and tales, and even a Minecraft monster. But his most recent appearance is much darker: according to news reports, a pair of 12-year-old girls have claimed that they stabbed a classmate 19 times in order to prove themselves worthy of visiting his "mansion" in a Wisconsin forest. One apparently claimed that Slenderman could read her thoughts.

The Milwaukee-Wisconsin Journal Sentinel and various other sites quote a police report in which the girls describe finding Slenderman on the Creepypasta Wiki, a repository of stories that, in its words, are "designed to unnerve and shock the reader." They allegedly planned to murder their victim — another 12-year-old girl — for months, but she ultimately escaped and, as of Monday night, was "fighting for her life" in a hospital. The two perpetrators are being charged as adults.

"We are a literature site, not a crazy satanic cult."

As John Herrman points out in The Awl, news reports have been ambivalent about what exactly Slenderman is. He's been variously referred to as a "mythological demon-like creature," a "prevalent internet myth," and "a fictional character." These range from extraordinarily wrong to not quite right. Creepypasta occupies a place somewhere between fiction, myth, and joke, and it's extremely varied — the girls' claim that Slenderman was "the 'leader' of Creepypasta" notwithstanding. Its stories carry a veneer of reality, written as first-person accounts, forum posts, or long-lost documents. They can be almost indistinguishable from tales you'd tell around a campfire, or they can become sprawling community projects that look a lot like alternate-reality games.

The Holders Series may be the most elaborate of these, comprised of several hundred entries based around dark rituals and quests. The quests are virtually impossible to begin, let alone complete. It provides a formula that, taken at face value, tells real-world readers to do terrible things. But that formula is equally adaptable to a ritual for becoming the Fresh Prince of Bel-Air. The infamously terrible creepypasta "WHO WAS PHONE" became a catchphrase so common that the operator of one site had to ban comments referencing it. At this point, Slenderman — a tall, thin, and faceless thing shown in the background of the photo above — is essentially a folk character who has gone through many variations since his first appearance. He's the Cthulhu of the 21st century.

In response to concerned parents, the Creepypasta Wiki has published a statement emphasizing that everything in it is clearly made up. "Something like this was bound to happen, considering the size of the Creepypasta community. All it takes is one person to do something insane and radical in the name of someone or something," it says. "There is a line of between fiction and reality, and it is up to you to realize where the line is. We are a literature site, not a crazy satanic cult."