Aaron Mahnke

The Romans attributed the condition to both an incubus and a succubus.

Egyptians sometimes attribute their sleep paralysis to djinn, which comes from Muslim folklore and gives us the idea of the genie, while Cambodians believe in ghosts that quite literally strangle their sleeping victims.

And in Catalonia, sleep paralysis has long been attributed to a creature that takes the appearance of a black dog or cat and sits on the person's chest.

In 1666, a Dutch physician named Isbrand van Diemerbroek echoed the popular belief that sleep paralysis was caused by the migration of external vapors into the head, but he also added another interesting piece to the puzzle.

You see, despite being an educated man, he called sleep paralysis, and I quote, "...incubus or the nightmare."

Now, when he wrote out nightmare, it wasn't all one word.

Instead, it was two, night and mare.

It seems that he wasn't referring to a bad dream like we might today.

He was writing about an actual supernatural being.

And he wasn't alone.

Across large swaths of Europe, people believed that those who suffered from sleep paralysis were being tormented by a mare, also called the mar or the mara.

Some people believe that it was a malicious spirit, while others thought that it was a sorcerer who enjoyed using their powers to torment people.

Old Norse stories claim that the Mara would ride people while they slept.

And in a Norwegian folktale, we learn of a queen who summoned a mare to crush her husband in his sleep.

Now, despite the horse-like imagery that the word mare might evoke for modern audiences, they weren't usually depicted as horses.

Instead, they were described as women.

But no matter what sleep paralysis looks like for each individual, there's one trait everyone seems to agree with, that it's absolutely terrifying.

And if you believe everything your sleep paralysis tells you, then you just might find yourself face-to-face with a nightmare of a very different kind.

Over the course of just five decades, the Duchy of Lorraine saw nearly 3,000 witch trials.

Now, to be fair, this 50-year window came right at the height of the European witch panic, so it might be tempting to cut them a little slack.