The most underrated Doctor Who two-parter that tested the Doctor's faith

Across its long run, Doctor Who has thrown strange and powerful foes at its Time Lord. Twenty years ago, during season 2 of the 2005 revival, the show pushed the Doctor in the two-part story 'The Impossible Planet' and 'The Satan Pit.' David Tennant and Billie Piper play the Tenth Doctor and Rose Tyler, who arrive at a sanctuary on Krop Tor - a planet orbiting a black hole - where a human expedition is drilling to learn what keeps the world from falling in.

The team has also enslaved a telepathic alien race, the Ood, leaving them vulnerable to a creature called the Beast. The Beast awakens, possesses Toby (Will Thorp) and then the Ood, and bodies begin to pile up. Although the two-parter didn’t match the viewing highs of the episodes immediately before or after it, it was ahead of its time in putting the Doctor, usually the cleverest person in the room, on the back foot.

The antagonist is a figure long associated with dread: the Devil.

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