 As the show progressed, key episodes, called parts of the "Mytharc", were recognized as the "mythology" of the series canon; these episodes carried the extraterrestrial / conspiracy storyline that evolved throughout the series. "Monster-of-the-Week" — often abbreviated as "MOTW" or "MoW" — came to denote the remainder of The X-Files episodes. These episodes, comprising the majority of the series, dealt with paranormal phenomena, including cryptids and mutants; science fiction technologies; horror monsters; and satiric / comedic elements. The main story arc involves the agents'efforts to uncover a government conspiracy to hide the existence of extraterrestrials on Earth and their sinister collaboration with those governments. Mysterious men comprising a shadow element within the U.S. government, known as "The Syndicate", are the major villains in the series; late in the series it is revealed that The Syndicate acts as the only liaison between mankind and a group of extraterrestrials that intends to destroy the human species. They are usually represented by Cigarette Smoking Man (William B. Davis), a ruthless killer, masterful politician, negotiator, failed novelist, and the series' principal antagonist.
