The Iscariot Organization, named after Judas Iscariot, the apostle who betrayed Jesus, is a top-secret wing of the Vatican (the section that's not supposed to exist) charged with the active pursuit and extermination of demons (such as vampires) and heretics. Given that the Hellsing Organization not only employs vampires but is run on the principles of staunch Protestantism, Iscariot is their natural rival, despite their similar aims.