Eugene Victor Tooms, the first Monster of the Week villain
Monster of the Week, or MOTW, refers to episodes of The X-Files that usually deal with some type of supernatural or paranormal creature/entity, but may also be a simple criminal with a unique ability. They are usually separate from episodes dealing with the Conspiracy, although certain elements can crossover between the two. Monster of the Week episodes populate the majority of each season, as to avoid the risk of over exposing the mythology arc.