15-year-old Anissa Weier has pled guilty to stabbing a classmate 19 times to appease the fictional, disturbing internet character Slender Man. She was charged with attempted first-degree murder, but has admitted to the lesser charge of attempted second-degree intentional homicide as party to a crime with a deadly weapon.

Weier, from Waukesha, Wisconsin, admitted to plotting the sacrificial killing of her friend Peyton Leutner. It’s reported that Weier and Morgan Geyser, then 12-years-old, lured their victim to a forest where they held her down and stabbed her multiple times, leaving her for dead in 2014. Miraculously, Leutner was able to crawl out of the woods, where she was found by a passer-by. She has since recovered from her serious wounds, and is back in school. The two assailants told police at the time they were trying to become “proxies” of Slender Man, who they had read about in online forums.

“I believed that if I didn’t go through with it, Slender Man would come and attack and kill myself, my friends and my family,” Weier told Waukesha County Court. “Those I cared about the most.”

Slender Man began to appear online around 2009 as a meme born from the online horror story page Creepypasta. The term “proxies” floats around stories of the creature, defined as those he chooses to do his bidding. His infamy is based off pseudo-documentary footage, pages and pages of fan-fic and photoshopped images of a tall, thin, faceless man who preys on people.

As AP reports, Geyser has been diagnosed with early-onset schizophrenia, and will face her own trial in October after pleading not guilty in 2016. Now Weier has entered a guilty plea, she will go to a trial which will examine the impact her mental health has had on her actions. If she’s found responsible, she can face up to 10 years in prison. If she’s deemed not legally responsible, she will spent three years in a mental health facility. Both Geyser and Weier’s trial will have sequestered juries – meaning they will be kept in isolation – because their cases have such high public interest.

A film about the creepy myth has been confirmed for release in 2018. The story of the disturbing real-life events was chronicled in the HBO documentary Beware the Slenderman.