Horror films are movies that strive to elicit fright, fear, terror, or horror from viewers. In horror film plots, evil forces, events, or characters, sometimes of supernatural origin, intrue into the everyday world. Horror movies usually include a central villain. Early horror films often drew inspiration from characters and stories from classic literature, such as Dracula, Frankenstein, The Mummy, The Wolf Man, Phantom of the Opera and Dr. Jekyll and Mr. Hyde. Later horror films, in contrast, often drew inspiration from the insecurities of life after World War II, giving rise to the three distinct, but related, sub-genres: the horror-of-personality film, the horror-of-Armageddon film, and the horror-of-the-demonic film. The last sub-genre may be seen as a modernized transition from the earliest horror films, expanding on their emphasis on supernatural agents that bring horror to the world.