DC Comics is one of the largest and oldest American comic book companies, and produces material featuring numerous well-known heroic characters including Superman, Batman, Wonder Woman, Green Lantern, The Flash, Aquaman, Hawkman, Hawkgirl, Green Arrow, Martian Manhunter, Cyborg, Static, Zatanna, and Shazam. Most of their material takes place in the fictional DC Universe, which also features teams such as the Justice League, the Justice Society of America, the Suicide Squad, and the Teen Titans, and well-known villains such as the Joker, Lex Luthor, Darkseid, Catwoman, Ra's al Ghul, Deathstroke, Reverse-Flash, Sinestro, Black Adam and Brainiac. The company has also published non-DC Universe-related material, including Watchmen, V for Vendetta and many titles under their alternative imprint Vertigo.