10 Best One-Time Only Doctor Who Villains

Who doesn't love a good old fashioned murder mystery?

Doctor Who did one with a twist in Mummy on the Orient Express, in which the Twelfth Doctor hops aboard the titular train for one last hurrah with Clara... only to discover that the passengers are dropping like flies at the hands of an invisible entity.

And that final point is just one of the reasons why the Foretold - which resembles an ordinary Egyptian mummy - is such a fantastic monster.

Because the only people who can see it are the ones that it's about to kill, there are a few great scenes in the episode where the soon-to-be victims of the Foretold are scared out of their minds and desperately trying to escape, while everyone else in the carriage thinks they're just going mad for no apparent reason.

It's unnerving stuff, and the ingenious decision to add an onscreen countdown - ticking away the seconds until the Foretold's next kill - adds to that sense of dread.

In the end though, it's revealed that the "mummy" is actually a dead soldier, and those bandages it's draped in? They were used to heal his wounds when he was still alive. It's a neat little twist that makes you view the entire episode in a different light, turning a mindless killing machine into a tragic and severely misunderstood bad guy.