In a world of alien invasions, powerful sorcerers, vast shadowy conspiracies and ancient gods, the galaxy's most powerful superheroes return to protect the universe.   Since the world's greatest heroes banded together as the Justice League to battle threats too great for any single hero to handle, they've saved the world countless times from unimaginable dangers. But the price has been high. Their ranks have diminished after fighting off an alien invasion and, with new dangers arising at an ever-increasing pace, the remaining crime fighters realize that protecting the entire world is going to take more technology and more manpower. A lot more.  Superman, Batman, Wonder Woman and Green Lantern continue to lead the universe's most powerful superheroes, along with such renowned defenders as Hawkgirl, the Flash and Martian Manhunter, calling in favors from Green Arrow, the Atom, Hawk and Dove and Zatanna, among others. Together, these fearless fighters are the Justice League Unlimited.