Wikipedia
"Dæmonicus" is the third episode of the ninth season of the American science fiction television series The X-Files and the show's 185th episode overall. It first premiered on the Fox network in the United States on December 2, 2001. The episode was written and directed by executive producer Frank Spotnitz. The episode is a "monster-of-the-week" episode, a stand-alone plot which is unconnected to the mythology, or overarching fictional history, of The X-Files. The episode earned a Nielsen rating of 5.5 and its premiere was viewed by 5.80 million households. The episode received mixed reviews from television critics.
The show centers on FBI special agents who work on cases linked to the paranormal, called X-Files; this season focuses on the investigations of John Doggett ( Robert Patrick), Monica Reyes ( Annabeth Gish), and Dana Scully ( Gillian Anderson). In this episode, Doggett, Reyes, and Scully investigate a series of bizarre killings that seem to be due to demonic possession but which Doggett believes is a hoax. The agents soon meet Josef Kobold ( James Remar), a man who seems to be playing some sort of demonic game.
"Dæmonicus" was written by Spotnitz to develop the new settings for the show's Monster-of-the-Week episodes, as well as the series in general. One of the major steps taken was to move Scully from the X-Files office to the FBI Academy at Quantico. When creating Josef Kobold, the episode's antagonist, Spotnitz researched various crimes and criminals, until he learned about Caryl Chessman, a man who had been sentenced to death on a technical charge of kidnapping. Series co-star Robert Patrick had issues remembering and delivering his lines, due to the theme of demonic possession, which reportedly made him uneasy.