Police in Wisconsin say two 12-year-old girls stabbed their friend nearly to death to please a mythological creature named "Slender Man."

The girls, who are facing charges of first-degree attempted homicide, learned about Slender Man from creepypasta.wikia.com, an online forum where users can post and share horror stories, according to police.

In a statement, the website said the allegedly myth-inspired stabbing is “an isolated incident and does not represent or attribute the Creepypasta community as a whole.

“This wiki does not endorse or advocate for killing, worship, and otherwise replication of rituals of fictional works,” the site administrator wrote.

“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 satanic cult.”

So who, or what, exactly is Slender Man?

Slender Man reportedly originated as an Internet meme that was submitted to the "Something Awful" forum in 2009 as part of an online competition to create photos containing mystical entities.

Two black and white photos showing groups of children standing with a tall, faceless figure in a black suit were submitted to the forum by a user named "Victor Surge."

To accompany the photos, the poster submitted a fake newspaper article about some children who had gone missing during a fire. The Slender Man was photoshopped into pictures of the scene, causing the fictional character to go viral, explained Shira Chess, an assistant professor of new media at the University of Georgia.

“Other forums really liked this character and began to develop (it) and sort of built it (up), much in the way folklore happens,” said Chess

To accompany the photos, the poster submitted fictional phrases suggesting that "The Slender Man" was linked to the disappearances of children.

Creepypasta describes Slender Man as a very thin man with extremely long limbs who can outstretch his arms and torso “to inhuman lengths in order to induce fear and ensnare his prey.”

“To be fair, the (stories) weren’t all about violence,” adds Chess. “Most were just sort of creepy.”

The character is said to have a pale, ghostly face with vague features. Some versions of the Slender Man story also describe him as having long black tentacles that protrude from his back.

What inspired the Slender Man myth?

According to the Know Your Meme website, Slender Man stories may have been inspired by a purported “Great Man” character in German mythology, a series of amateur adventure games that reference a character named “The Tall Man,” or postings on 4chan, an online image board.

Slender Man film

Know Your Meme also notes that a young filmmaker, AJ Meadows, sought to raise $10,000 on Kickstarter to complete a movie project about the Slender Man myth.

The movie was released online in February 2013, but removed from the web due to a copyright issue, according to the website.

The Slender Man was also referenced in a season 9 episode of the popular American paranormal drama called “Supernatural.” At the end of the episode, the Thinman, as the character was called, was proven to be a hoax and a cover for a pair of serial killers.