Horror movies based on even scarier true stories

"Based on a True Story": it's the oldest trick in Hollywood marketing, and horror fans have read variations on those words countless times. Whether a movie actually delivers scares on its "fact-based" premise is one of the great crapshoots of horror fandom, but the gimmick has been a pretty safe bet at the box office. The blurrier the line between fact and fiction, the bigger the potential scares—but sometimes, the stories behind the scenes are even more terrifying. From the pathological to the paranormal, here are few of the truly terrifying stories that inspired the genre's most memorable scares.

Bram Stoker's classic story has been revisited countless times in cinema, making it some of the most beloved source material of all time, but until Francis Ford Coppola's film Bram Stoker's Dracula, the connection between Dracula and the historical figure Vlad Drac had never been depicted onscreen. If you think a pale, immortal vampire poised to suck your blood is scary, consider "Vlad the Impaler": the Transylvanian noble is thought to have tortured and executed as many as 100,000 peasants and civilians during his reign. Deeming the poor as "useless to society," he had them slowly impaled from rectum to cranium, and then hoisted publicly for display. So….which is scarier: the fang or the pole?