This book features the classic crossovers between the Justice League and their predecessors the Justice Society of America that launched the DC Multiverse as we know it! This collection brings features adventures of the heroes of two Earths as they search through time for the Seven Soldiers of Victory, discover of Earth-X and the Freedom Fighters, meet the heroes of Earth-S, led by the Earth's Mightiest Mortal, Captain Marvel, as well as the Legion of Super-Heroes!