Infinite Crisis was a sequel to DC's 1985 limited series Crisis on Infinite Earths. It revisited characters and concepts from that earlier series, including the existence of the DC Multiverse, with alternative versions of such iconic characters as the Golden Age Earth-Two Superman. A major theme was the nature of heroism, contrasting the often dark and conflicted modern-day heroes with memories of "lighter" and ostensibly more noble and collegial heroes of American comic books' earlier days.