Wes Craven’s “A Nightmare on Elm Street” has had a huge impact in horror. But where did it come from? Well the story was inspired by a very real and very scary phenomenon in the 70s and 80s. A group of men suddenly died in their sleep after being visited by a nightmare demon known in their culture as Dab Tsog. Experts still don’t fully understand what happened to these men. Could it really have been a sleep demon?