A Masked Mystery Villain is a stock character in genre fiction. The Masked Mystery Villain was frequently used in the adventure stories of Pulp magazines and Movie Serials in the early twentieth century. They can also appear in Crime fiction to add to the atmosphere of suspense and suspicion. The "Mask" need not be literal (although it often is), referring more to the subterfuge involved.
He or she is the often main antagonist of the story, often acting behind the scenes with henchmen confronting the protagonists directly. Usually, the protagonists must discover the villain's true identity before they can be defeated. Often the Masked Mystery Villain will turn out to be either one of the protagonists themselves or a significant member of the supporting cast. The author may give the viewer or reader clues, with many red herrings, as to the villain's identity - sometime as the characters find them and sometimes for the audience alone. However, the identity is not usually revealed to the audience before it is revealed to the characters of the story. Even the villain's henchmen rarely know the truth about their master.
The concept was reversed in the serials "The Lone Ranger" and "The Masked Marvel", where the true identity of the hero is unknown and a number of characters remain possible candidates until the end.
The archetype tends to be a popular one to be parodied, often using a literal mask and breaking into a stereotypical evil laugh.
Examples of Masked Mystery Villains 
Computer and video games