James Moriarty

James Moriarty was the arch-enemy of Sherlock Holmes.

History
In order to investigate Baron Maupertuis, Moriarty used the alias O'Connor and donned a ginger wig as part of his disguise. He also wrote a paper on the mathematics of folding higher dimensions. (PROSE: All-Consuming Fire) Moriarty died in 1893. (PROSE: The Found World)

Contradicting other accounts, Moriarty also seemed to exist in the Land of Fiction, suggesting he was a fictional character. (COMIC: Character Assassin)

The Eleventh Doctor, while dressed like Sherlock Holmes, once compared the Great Intelligence to Moriarty, calling it "the clever one." (TV: The Snowmen)

Behind the scenes
In 2010, Steven Moffat and Mark Gatiss created the BBC Wales series, starring Benedict Cumberbatch as Sherlock. Steve Thompson is the third main writer of the series. In their version, "Jim" Moriarty, played by, is a recurring character, featuring in the series finales of all three seasons so far.

It has often been suggested that The Master was inspired by the Moriarty character.