Two 12-year-old Wisconsin girls, each facing up to 65 years in prison for allegedly stabbing a friend nearly to death on Saturday, said the gruesome act was motivated by an Internet urban legend.

Morgan Geyser and Anissa Weier told investigators that they lured their friend, who has not been named, into the woods near Geyser’s home in the southeastern city of Waukesha. They said they planned to murder the friend to pay homage to a mythical figure known as “Slender Man” or “Slenderman.”

The girls had read about Slender Man on the horror storytelling website Creepypasta Wiki, they said.

Described by BBC Radio 4 commentator Aleks Krotoski as the “first great myth of the web,” Slender Man is a paranormal figure with a featureless face who wears a black suit and has tentacle-like arms protruding from his back. Urban legend has it that Slender Man lives in the forest and has the ability to teleport.

Slender Man, who belongs to a growing variety of Internet folklore figures, is arguably the most frequently encountered Internet-borne ghoul out there. He appears in countless digital tales, video games and visual art posted all over the Web.

Geyser and Weier were charged on Monday in Waukesha County Circuit Court as adults with attempted first-degree murder. According to the criminal report, the girls, who attended Horning Middle School with the victim, stabbed their friend 19 times in her arms, legs and torso after inviting her to play a game of hide-and-seek in the woods.

One girl held the victim down and encouraged the other to “go ballistic.” She began to stab the victim repeatedly while the victim screamed, Associated Press reports.

Despite having been severely injured, the victim managed to crawl to a nearby road where a bicyclist noticed her. She was rushed to a hospital where doctors said she had barely survived.

Police took the two suspects into custody shortly after.

The 12-year-old girls told investigators that they thought killing the victim would make them proxies of Slender Man, whom they believed lives in a mansion in the Nicolet National Forest in northern Wisconsin, Milwaukee-Wisconsin Journal Sentinel reports. The girls said they planned to visit Slender Man after murdering their friend, and even packed a backpack full of granola bars and water bottles for the trip.

"As the details became more apparent, it's extremely disturbing as a parent and as a chief of police, especially with the age of the suspects and being female," said Police Chief Russell Jack, according to USA Today. "This is a very disturbing investigation."

Creepypasta gets its name from the Internet slang “copypasta,” which refers to a chunk of text that gets reproduced over and over again on the Web, typically through online discussion forums and social networking sites.

Weier told investigators that she introduced Geyser to Creepypasta in December, and that the girls later agreed they needed to kill someone to prove themselves to Slender Man.

Creepypasta responded to the gruesome stabbing with a blog post.

“This is an isolated incident, and does not represent or attribute the Creepypasta community as a whole,” a user who goes by the name Sloshedtrain wrote. “This wiki does not endorse or advocate for the killing, worship, and otherwise replication of rituals of fictional works … We are a literature site, not a crazy satanic cult.”