Professor James Moriarty is a fictional character in some of the Sherlock Holmes stories written by Sir Arthur Conan Doyle. Moriarty is a criminal mastermind whom Holmes describes as the "Napoleon of crime". Doyle lifted the phrase from a Scotland Yard inspector who was referring to Adam Worth, a real-life criminal mastermind and one of the individuals upon whom the character of Moriarty was based. The character was introduced primarily as a narrative device to enable Conan Doyle to kill off Sherlock Holmes, and only featured directly in two of the Sherlock Holmes stories. However, in more recent derivative work he has been given a greater prominence and treated as Holmes' archenemy.