10 Doctor Who Villains With Terrifying Abilities

While any old villain with murderous intent and a pair of hands could suffocate someone in their sleep, it's the occult nature of the Mara that ranks this as a particularly deadly ability.

The Mara is an evil entity that resembles a snake in its true form, but more often than not, it chooses to reside within the minds of its victims, possessing them and making them commit sinister deeds. This makes the villain a tough one to stop - it's a bit like fighting a ghost, or some other abstract force.

In the Torchwood episode Small Worlds, Captain Jack Harkness remarks on the Mara's legendary evil, claiming that the name "Mara" is where the word "nightmare" comes from. At the same time, he also notes that the Mara will "suffocate people in their sleep", which, again, doesn't sound all that scary as far as abilities go.

But considering the Mara's status as a psychological meddler, Jack clearly isn't referring to the physical act of suffocation. He's describing a creature that can infest your dreams and attack you while you sleep, a bit like Freddy Krueger - only this version of Freddy can't be fought off via traditional means.

Unless you dream about mirrors, of course.