During the 1950s, DC Comics editor Julius Schwartz gave the company's comic book heroes a reboot, following a decline in popularity during the Second World War. Beginning with Showcase #4 in 1956, a new incarnation of the Flash, Barry Allen made his debut, leading to a revival of Golden Age characters, but with different identities and origin stories. The new Silver Age would also bring about new versions of Batman, Superman and Wonder Woman, but with their histories retained. It was with the publication of the story, "Flash of Two Worlds" in The Flash #123 , which saw the first appearance of the Multiverse, where Barry Allen met the original Golden Age Flash, Jay Garrick. The success of the crossover led to annual crossovers between the older Justice Society and the newer Justice League, with the two groups of heroes existing on different Earths: the Golden Age heroes living on Earth-2 and the Silver Age heroes living on Earth-1. The concept of parallel Earths, with different historical events and people became a defining characteristic of DC Comics lore, as writers were able to use the Multiverse to help explain continuity errors and retcon stories. Furthermore, the acquisition of other comic book companies and their characters by DC were incorporated into the Multiverse, including Earth-4 for Charlton Comics and Earth-S for Fawcett Comics.
As DC approached its 50th anniversary, a huge crossover was planned that was to feature virtually every character from DC Comics’ history. However, after decades worth of continuity, the company found many contradictory storylines and characters with inconsistent backgrounds, e.g. Superman was originally the only survivor of the planet Krypton, later being changed with the introduction of Supergirl and Krypto the dog. Further problems also related to the characters’ ages like Batman retaining his youth from the late 1930s to the 1980s and his sidekick Robin, taking 30 years of real time to graduate from high school. Writer Marv Wolfman took the anniversary crossover as an opportunity to simplify DC's narrative continuity by removing the Multiverse, leaving one, single Earth where all the heroes would exist.
The Multiverse is under attack! A mysterious being known as the Monitor transports heroes from across the Multiverse to save it from destruction by the expanding antimatter universe. The Anti-Monitor has returned and won't rest until all life has been eradicated.
Alexander Luthor Jr
The Flash/Barry Allen
The Flash/Jay Garrick
Wolfman saw Crisis on Infinite Earths , a 12 issue crossover, published throughout 1985, as a chance to clean up the muddled continuity that existed within DC since the company's inception. The word "crisis" was used to demonstrate that the story would be an interdimensional crossover in the style of the Justice Society/Justice League crossovers from years earlier. A full year of planning was involved, whereby a list of every DC character was catalogued and multiple meetings were had with company president Jenette Kahn, vice president and executive editor, Dick Giordano and the rest of the DC editors. How to use the character of the Monitor was discussed, with writers instructed to use the Monitor twice, but to only show his assistant, Lyla as the only on panel character.
The comic explains that the many storylines and continuity contradictions are part of a much larger Multiverse, containing an infinite number of parallel universes, featuring alternate versions of characters, with the main DC continuity taking place on Earth-1. A cosmic being known as the Monitor oversees the Multiverse, ensuring that the vibrational frequency that separates each Earth remains intact. Across the multiple Earths, shadow demons begin attacking cities and wreak havoc on the populace. On the Monitor's command, his assistant, Lyla, aka Harbinger searches the Multiverse to gather the greatest heroes across reality. As more worlds fall, the Monitor's fear is confirmed: his evil counterpart, the Anti-Monitor, who exists in his own antimatter universe, has awoken and is systematically destroying the Multiverse to expand his own universe. In a shock twist, Harbinger, possessed by one of the Anti-Monitor's demons, kills the Monitor, however, the Monitor planned for this and his death releases a wave of energy to move the last five parallel Earths into a protective limbo dimension. However, the vibrational frequencies that separate the Earths begin to break down causing the planets to merge. Overcome with guilt, Harbinger rallies the heroes to lead an assault on the Anti-Monitor in the antimatter universe, using Alexander Luthor Jr’s power to open a portal between universes. The heroes reach the Anti-Monitor's fortress, destroying a machine designed to eradicate the five remaining Earths; although Supergirl sacrifices herself to save her cousin, Superman from the Anti-Monitor. While the Anti-Monitor retreats, Lex Luthor and Brainiac use the opportunity to conquer the Earths, but their attempts to unite the villains proves cumbersome as they quickly turn on each other.
Meanwhile, the Flash is trapped in the Anti-Monitor's lair and learns of his latest attempt to destroy the Multiverse by using an antimatter cannon to penetrate the limbo universe and destroy the remaining Earths. Barry too gives up his life to destroy the cannon and foil the Anti-Monitor’s scheme. Following two setbacks, an enraged Anti-Monitor vows revenge and travels back in time to annihilate the Multiverse. They heroes give chase, travelling back to the dawn of time to confront him. When it looks as though the Anti-Monitor has finally won, the Spectre arrives and overloads the matter/antimatter energy reaction, shattering space and time. The Multiverse collapses and is reformed into a single Earth. The world now contains many heroes, whose Earth no longer exists and struggle to find a place in society, with those only present at the dawn of time remembering the original realities. The shadow demons repower the Anti-Monitor, who tries to wipe out the new Earth, but is stopped in a counter-attack, leading to a final battle with Earth-2 Superman, Superboy-Prime, Alexander Luthor Jr and Darkseid. The Anti-Monitor is reduced to a flaming skull and dies in a nearby star. As the portal to the positive matter universe has been sealed forever, Alexander takes the group (with the exception of Darkseid) into their own pocket dimension. The heroes of Earth commemorate their fallen comrades, looking to the future for hope and inspiration.
Crisis on Infinite Earths had a huge impact on DC Comics legacy, with the ongoing narrative continuity being split into Pre-and Post-Crisis time periods. The single Earth that remained after the Multiverse had disbanded was designated New Earth and all major characters were given revamped origins such as John Byrne's The Man of Steel , resetting Superman's backstory. Barry Allen's death provided long-lasting ramifications going forward since it was the first time a significant character had been killed off. Wally West, the previous Kid Flash became the new Flash and wore his mentor’s costume. Wally would remain the Flash throughout the 1990s until Barry Allen's return in The Flash: Rebirth in 2009. Crisis on Infinite Earths would form the beginning of a trilogy, continuing with Infinite Crisis in 2005 and concluding with Final Crisis in 2008. Crisis on Infinite Earths is a milestone work, having to deal with decades of conflicting continuity and effectively having to wipe the slate clean. Although at times there are some pacing issues and the comic would flow better with 10 issues instead of 12 (the Luthor/Brainiac alliance is very much filler), the comic is a triumph at what it sets out to do. The DC universe was remade anew, ready for more fantastical adventures.