Here's what you need to know about The Slender Man, which went from Internet fiction to urban legend before influencing real - life horror.

In 2009, Eric Knudsen participated in a Photoshop thread on the SomethingAwful forums that asked users to create paranormal images. Knudsen took existing photographs and added his own creation, 'The Slender Man,' a man with no face, impossibly long limbs, and a black suit. Knudsen also wrote a small backstory for the creature, claiming that it was responsible for the disappearance of children. The Slender Man was extremely popular with other users, and it didn't take long for this new 'digital Bogeyman' to become a hit online, reused in various memes and websites before becoming the center of a number of YouTube web series. There's a very good chance that most young people you talk to today will know about the Slender Man and the mythology that has built up around it.

In 2014, two 12 - year old girls stabbed a friend 19 times. They later told police that they were trying to offer their friend's life as a sacrifice to The Slender Man so that they could become his 'proxies,' or servants.The two girls may face up to 65 years in prison if convicted of intentional homicide.

While both girls have now been diagnosed with mental disorders, the HBO documentary 'Beware The Slender Man' explores just how dangerous the Internet and imagination can be for adolescents with proper guidance from their parents or other adults. Though there is no real 'Slender Man,' there is a very real problem with young people who turn to the Internet when facing feelings of isolation, loneliness, and depression. It might be a good idea to talk to your kids about the Slender Man and what other sites they visit online.