Two years ago, the world was left stunned after a 12-year-old girl was stabbed 19 times by her two closest friends after being lured out into the woods during a slumber party. 

According to the pair, who have both been diagnosed with mental illness, they were told to commit the atrocious crime by the infamous internet creation, Slenderman

HBO has since made a documentary centering on the incident while also exploring the darkest corners of the internet and how they influence children’s thoughts.

Titled Beware the Slenderman, the first trailer for the Irene Taylor Brodsky directed documentary has arrived online, splicing together footage from the trial and CGI renderings of the faceless fictional boogeyman. 

Slenderman, also known as Slender Man,was originally created in 2009 as part of a Photoshop competition on the internet forum Something Awful. 

The goal was to make normal photographs appear paranormal, with one user submitting two black and white photos depicting groups of children to which he added a tall, faceless figure wearing a black suit.

Soon after, the posts went viral, with fanart, cosplays and online fictional stories about the Slenderman being created: famously, a video game - titled  Slender: The Eight Pages - was released in 2012 and has since been downloaded over two million times. 

Beware the Slenderman airs on HBO 23 January 2017.