Batman and Green Lantern encountered each other during a battle against a Parademon in Gotham City. After realizing the creature was extraterrestrial in origin, the two heroes went to Metropolis to seek out Superman. Later, the Flash arrived and they moved to an abandoned building to work on analyzing a mysterious alien box, when it suddenly activated and more Parademons arrived. While fighting the Parademons, Aquaman and Wonder Woman appeared and join forces with the other heroes. The mysterious box led to Darkseid's arrival on Earth, and the heroes came together, along with the newcomer Cyborg, to defeat him. The public becames enamored with the heroes, and a writer dubbed the group the Justice League.