The “Slenderman” has been an urban legend since it was born in June 2009. The creator: artist Eric Knudsen, going under the nom de plume Victor Surge, on an online forum called Something Awful.
The story has since influenced everything from Halloween costumes to video games to documentaries. It also, allegedly, inspired a pair of very real pre-teen girls to stab their classmate. Their trials are set to start this year.
Here’s everything you need to know about the creepy cultural touchstone.
The Slenderman origin
In 2009, the web forum Something Awful held a contest challenging users to edit everyday photographs to appear paranormal.
Knudsen submitted two black-and-white photos of children with a newly-created “Slenderman” character lurking in their backgrounds.
Intent: "Unease and terror"
Knudsen later told the website Know Your Meme that his intent for the character was “something whose motivations can barely be comprehended, and [which caused] unease and terror in a general population.”
Slenderman: appearance and influences
Knudsen depicted the character as an abnormally tall, thin man, with a featureless face.
Knudsen said he was inspired by Stephen King’s “The Mist,” among other fictions.
The mythology grows
Just days after Knudsen created Slenderman, other users started to layer their own attributes onto the character.
Some suggested Slenderman has tentacles sprouting from his back; that he can cause amnesia; and that he can be seen hiding in woodlands or stalking children.
Unlike many other fictional characters, Slenderman isn’t seen as having a single creator.
Therefore, he has no official canon; his appearance, motives and abilities differ depending on the storyteller. Here’s an interpretation by gamemaker Parsec Productions.
A popular Halloween costume
In fact, Slenderman has become such a popular figure in pop culture that many people have decided to dress as the eerie fictional entity for Halloween.
Enderman on Minecraft
On the popular game Minecraft, there are 3-block tall characters called Endermen. Due to their long, skinny bodies and similar name, they have drawn comparisons to the Slenderman.
Slenderman video games
That isn’t the only Slenderman-themed video game connection. There have also been entire games: “Slender: The Arrival” and “Slender: The Eight Pages.” The latter, released in 2012, was downloaded two million times within its first month.
A terrible accusation
On May 31, 2014, two girls—Morgan Geyser (right) and Anissa Weier, both 12 at the time—allegedly brought a 11-year-old classmate to the woods behind Geyser’s home in Waukesha, Wisconsin.
The two girls then allegedly stabbed their classmate 19 times in what investigators described as a sacrifice intended to please Slenderman, which they had discovered on a horror story website. One of the girls reportedly told a detective they were trying to become “proxies” of Slenderman.
The victim survived
The victim, who was left for dead, managed to crawl to a bike path, where she was saved by a bicyclist.
Of the 19 stab wounds, two hit major organs, while one wound missed a major artery by less than a millimeter.
She spent six days in the hospital.
After a massive manhunt, the alleged attackers were apprehended close to Interstate 94. An officer found a knife believed to have been used in the stabbing in one of the girls’ bags.
HBO's "Beware the Slenderman"
In January 2017, HBO broadcasted the documentary “Beware the Slenderman,” which is based on the case.
The alleged attack was premeditated
According to “Beware the Slenderman,” the two girls had planned the attack for months.
Geyser temporarily ruled incompetent to stand trial
In August 2014, Geyser (pictured) was ruled incompetent to stand trial after being diagnosed with childhood-onset schizophrenia.
Then in December 2014, the pair were ruled competent to stand trial.
The two suspects have pleaded “not guilty by reason of mental disease or defect.”
Geyser's mental state
Geyser’s diagnosis reportedly stemmed from her belief that she has mind-control powers. She also indicated that she speaks with fictional characters, including Voldemort from the Harry Potter series.
The alleged attackers will be tried as adults
After two years of legal battles, the Wisconsin Appeals Court ruled that Geyser and Weier would be tried as adults, based in part on signs that the crime was premeditated.
Prosecutors said Geyser and Weier apparently believed that if they sacrificed someone to the Slenderman that the character would spare the girls’ families lives and invite the pair to live in his “Slender Mansion.”
"Beware the Slenderman" interrogation footage
“Beware the Slenderman” showed portions of the police interrogation of both Weier and Geyser. In describing the incident, Geyser said that stabbing her friend “didn’t feel like anything. It was like … air.”
The girls could face 45 years in prison
If convicted of attempted first-degree intentional homicide, each girl could receive a sentence of up to 45 years in state prison.
The trial is set to start this year.
More alleged Slenderman crimes
On September 4, 2014, a 16-year-old girl from Port Richey, Florida, allegedly set her house on fire in what may have been a Slenderman-related incident.
Eddie Daniels of the Pasco Sheriff’s Office told ABC News: “She had visited the website that contains a lot of the Slenderman information and stories. It would be safe to say there is a connection to that.”
Ohio teen allegedly attacks mom
In June 2014, a Hamilton County, Ohio, mom was allegedly attacked in the kitchen by her 13-year-old daughter.
The mom, who declined to identify herself, told Cincinnati news station WLWT, “We found things that she had written and she made reference to Slenderman.”
The alleged attacker reportedly said she attacked her mother to please Slenderman, per a criminal complaint obtained by CBS News Crimesider.
Meanwhile, the popularity of Slenderman continues to grow.
As of March 2017, the YouTube page for “Marble Hornets” — a Slenderman-inspired drama series— had more than 448,000 subscribers and 92 episodes.