Crisis on Infinite Earths (1985): The Trope Namer and Trope Codifier. Before CoIE, there were two major and nearly a dozen minor separate DCU "Earths"/realities, each with its own continuity. They didn't cross over, except when they did (or when a DC writer forgot who was supposed to be on which Earth and a DC editor didn't catch the goof). Afterwards: one Earth, one reality, and the biggest retconning of past events ever. Let one example serve for all: Pre-Crisis, there was Kara Zor-El, better known as Supergirl. During Crisis, she died. Post-Crisis, she had never existed due to the edict that, following the Man of Steelreboot, Superman was to the only surviving Kryptonian (although she did appear in the final arc of Peter David's Many Happy Returns and other places). To this day, nobody (save for a few people, namely Donna Troy and The Spectre) remembers her as she was then, though a new version of the character returned in The Supergirl from Krypton (2004) and her death was retconned in the Convergence event. The first act of the "Multiverse Saga" dealing with the "Death of the Multiverse".
Legends (1987): This series was a crossover in which the evil god Darkseid tries to turn humanity against all its superheroes; it doesn't take. Legends was most notable for launching the semi-humorous Justice League International (the one with Blue Beetle) and the perennially popular supervillains-doing-espionage title Suicide Squad, as well as starting the career of third The Flash, Wally West. It also marked the post-Crisis debuts of Wonder Woman (after she was rebooted from scratch by George Perez and Greg Potter) and Captain Marvel.
Three events in 1988:
In Cosmic Odyssey (ironically the only one that was self-contained), Darkseid, the New Gods, and a group of super-heroes fight a giant shadow that Metron claims is the Anti-Life Equation's true form. Outside of John Stewart (no, not that one) acting like a rookie and causing an entire planet to explode due to his hubris, no one likes to talk about this story since making the Anti-Life Equation a giant shadow monster was a stupid idea.
In Millennium (1988), the robotic Manhunters try to stop the Guardians of the Universe from giving a group of really bad ethnic stereotypes virtual Godhood; it doesn't work out. By contractual obligation, at least one secondary character from most of DC's titles turned out to be the Manhunters' molesnote (In Superman, basically all of Smallville but the Kents.), which was never mentioned again afterwords. Really, this event’s most lasting effect on the DC universe was said ethnic stereotypes spinning-off into their own short-lived series, The New Guardians, and the most lasting contribution that book had was the creation of the crack-powered supervillian Snowflame, an initially one-shot character who became such a memetic legend that he returned 32 years later in a Catwoman storyline.
In Invasion!, a whole mess of alien planets get together and try to take over Earth to keep all the superbeings we keep producing under control; yet again, it doesn't work out. This crossover also introduced the Metagene Meta Origin concept in the DCU, as well as led to the launching of Justice League Europe, L.E.G.I.O.N., a 20th Century Legion of Super-Heroes spin-off title known mainly for having Lobo and Brainiac 2 on the roster and serving as a Soft Reboot for Grant Morrison's critically acclaimed Doom Patrol run.
Two in 1991:
War of the Gods wasn't a bad idea in theory: All the different godly pantheons in The DCU (the New Gods, plus the Olympians, the Asgardians, etc.) have at it and the various divinely-powered superheroes (Wonder Woman, Captain Marvel, etc.) get caught up in it. Unfortunately, writer George Perez made the mistake of double-booking himself drawing Marvel's The Infinity Gauntlet and writing/drawing War of the Gods at the same time, leading to War of the Gods suffering from bad writing.
Armageddon 2001: One of DC's top super-heroes will become the uber-villain "Monarch"! Except the ending (it was Captain Atom) gets leaked, meaning third-string character Hawk became Monarch instead. Monarch promptly disappeared until three years later, when he was retooled as Extant and became a flunky for A-List hero Hal Jordan, who went evil in the wake of The Death of Superman.
Eclipso: The Darkness Within (1992): Over the summer, DC retconned a B-List villain from the '60s into a serious threat capable of possessing anyone — up to and including Superman. Very little changes, other than the Heroic Sacrifice of Starman IV — whose book had been canceled anyway (and it apparently didn't take). Eclipso himself got a series out of it for about two years, notable as one of the few mainstream comic series with a villain as its protagonist at the time.
Bloodlines (1993): Whether you like this or not all depends on if you're a fan of the Dark Age. This was a Cross Through of all of DC's Annual series for 1993. A race of Xenomorph-like parasites invade and start killing people by draining their spinal fluid. A small percentage of people, however, gained superpowers by this, leading to the creation of a new bunch of Nineties Anti Heroes. Nothing really changed and these new heroes were eventually reduced to cannon fodder for Infinite Crisis, or else ending up in Comic-Book Limbo. The only notable result from this crossover being Garth Ennis' Hitman. Aside from that, it's probably best remembered for crossing over with two far-better known DC stories from the same time period: The Death of Superman and Knightfall, due to featuring the four replacement Supermen and the Azrael-Batman for most of the crossover.
Worlds Collide (1994) (1994): This was a major DC Comics/Milestone Comics crossover, which had to be handled carefully, since the DC characters were comics in the Milestone universe. It was a scintillating series in that the differences between similar characters such as Superman and Icon were examined. Perhaps the most entertaining was the relationship between Hardware and Steel, who had the same abilities and skills, but were at opposite ends of the Sliding Scale of Idealism Versus Cynicism. Since then, Milestone was folded into the DC universe, which seems even more poignant after the passing of Dwayne McDuffie.
A more straight example for Milestone was Shadow War, which included all of the titles in the line, using it to introduce titles like Xombi and Kobalt.
1995's Underworld Unleashed saw Mark Waid killing off 90% of The Flash's rogue's gallery who he felt were too silly even for his Silver Age tastes (though this didn't last long and Waid was proven wrong in a BIG way later on) and introducing Neron, the de facto Satan of the DC Universe proper. It also saw a ton of DC villains selling their souls for grim and gritty revamps, of which only a small handful actually stuck.
In the afterword to the collected edition, Waid claims that killing and resurrecting the Rogues was the plan all along in order to protect them from unnecessary Darker and Edgier revision:
Brian and I arranged for them to lie low in hell for a little while, if only to keep some knuckleheaded creator from, oh, say, turning Heat Wave into a living pillar of fire.
Final Nightnote Not to be confused with either Final Crisis or Blackest Night (1996): is probably the most fondly-remembered crossover from the 1990s, most likely because the whole thing became one huge Author's Saving Throw/Last Hurrah for Hal Jordan (writer Karl Kessel agreed to write the story for DC on the condition that he could give Hal a mercy killing/heroic sacrifice death). An alien weapon called a Sun-Eater arrives in the solar system and, surprisingly enough, eats the sun. After Earth's heroes try to keep their sunless world alive, Hal Jordan make a Heroic Sacrifice to rekindle the sun and redeem himself (of course, Redemption Equals Death). Also, the Post-Zero Hour Legion meets everyone in the DC Universe proper for the first time — and before his death, Hal resurrects Green Arrow in the final issue of Chuck Dixon's run.
Genesis (1997): John Byrne "kills off" Darkseid in a lame plot where the Source Wall breaks and everyone's powers start acting wonky. Nobody cares. Moving on...
DC One Million (1998): All DCU books stopped and became "<Title> #1,000,000" as the JLA and the rest of the DC Universe go into the future to fight Solaris the Sentient Sun, who wants to kill his creator Superman. As Grant Morrison stories go, you'll either love it or hate it. This crossover is certainly part of the main DCU canon (Hourman One Million becomes a major player in JLA, JSA and his own book). (The final issue of Morrison's later All-Star Superman features the present-day Solaris, and acts as a kind of origin story for the future society depicted in One Million — or rather, presumably an alternative version of that future society, since All-Star Superman is definitely not part of the main DCU canon.)
Day of Judgment (1999): Featured a then unknown Geoff Johns writing a story where the demons Neron and Etrigan steal the nigh-omnipotent powers of the Spectre. Hilarity Ensues, and the ghost of Hal Jordan ends up becoming the new Spectre. Led to the creation of the Sentinels of Magic - a group of DC's mystic heroes who then appeared absolutely nowhere.
Sins of Youth (2000): In an effort to promote Young Justice, DC produced this series, which was a special Crisis Crossover in which Young Justice, the JLA, the JSA, the Titans and as many others as the pencilers could cram into frame descended on the National Mall in Washington, D.C., for a rally, only to face the mother of all Fountain of Youth plots wherein nearly every character present was aged or de-aged. It only interrupted the monthly run of YJ and crossed over into Superboy, and was over within a month real-time, but the scale of the story and the villains' plot was worthy of this trope.
2001 had two events:
Our Worlds at War featured an Omnicidal Maniac trying to destroy the universe via destroying Earth (with Brainiac-13 pulling up the rear to exploit the madness) and the entire universe teaming up in a galactic alliance to save the universe. Infamous for it's massive number of deaths (Guy Gardner, Martha and Johnathan Kent, Aquaman, Sam Lane, and Wonder Woman's mom Hippolyta), just about all of which were overturned, with Gardner and the Kents being upgraded to living within months of the storyline ending.
Joker's Last Laugh, tied very much to the other crossover (almost literally starting after Our Worlds At War had ended). This story had Joker infect all of the DC Universe's villains with chemicals turning them into Joker-lite mass murderers, after Joker is falsely told he has terminal cancer. Two notable scenes are when Joker Lampshades previous crises by desiring red skies for his plan, and Chuck Dixon spending the entire storyline effectively cursing out readers for asking why no one kills the Joker.
Identity Crisis (2004) Identity Crisis: This was the first book to use "Crisis" in its title since Zero Hour. It was a crossover, but not necessarily a crisis crossover — in fact, it was a very low-key murder mystery far more concerned with buried secrets and the personal lives of heroes than with blowing stuff up — but it did end up changing things, due to the nature of the secrets revealed rather than any cosmic shenanigans. It's also notable as it deretconed back into existence many pre-Crisis story lines from the Silver and Bronze ages, but at the same time made them Darker and Edgier. It turned B-list Teen Titans Villain Dr. Light into a rapist, revealing that his "bumbling" and "pathetic" status was the result of a magically-induced lobotomy. The story was eventually revealed to be the first part of a trilogy to "explore the DC heroes" in which they were put up against "a very personal threat". Its repercussions were felt throughout The DCU (leading to mini-Crisis Crossovers such as Villains United and the Day of Judgement sequel Day of Vengeance) until they coalesced in:
Infinite Crisis (2005-2006): Refugees from the original Crisis, who had been watching the DCU since, had decided that the events of Identity Crisis and the things that followed were the last straw, and returned to the universe to "set things right". As their version of setting things right involved destroying reality and replacing it with a "better" one, the current inhabitants of the DCU were less than pleased with the plan. Fighting ensued, and in the end a "soft reset" occurred — some things were changed but by and large, continuity remained the same (except for the Legion of Super-Heroes, which received its second complete reboot) — and the multiverse, gone since the pre-Crisis days, returned. Served as the second act of the "Multiverse Trilogy" as the "rebuild of the Multiverse" and the second act of the "Exploration Trilogy" by "putting the greatest odds against the heroes". Was immediately followed by:
52 (2006-7): Basically the final act of the storyline of Identity Crisis and Infinite Crisis (story-wise). Innovative for its use of real time continuity, tossing Comic-Book Time out the window in favor of the 24 approach, published weekly, from May 2006 to May 2007, each issue represents a week of time in-universe, covering the "missing year" of the DCU, as after Infinite Crisis, all books were jumped forward "One year later". Written by a "dream team" of four writers (Geoff Johns, Greg Rucka, Mark Waid, and Grant Morrison) each of whom contributed something to every issue. It also followed the lives of minor characters of the DCU while the "Big Three" Batman, Superman, and Wonder Woman took the year off for various reasons, Widely considered to be one of the greatest story lines of the Modern Age. It also introduced the Modern Batwoman, and Renee Montoya as The Question.
Countdown to Final Crisis (2007-2008): Meant to act as a bridge between 52 and Final Crisis. It's remembered as one of the worst comic storylines of all time, having been hampered by constant Executive Meddling, which led to an oversaturation of tie-ins resulting in even worse Archive Panic (How bad? Another reviled event comic, Amazons Attack!, ties into it... and that event has tie-in issues of its own!), and the main comic itself was riddled with plotholes and bad art. DC quickly worked to move the whole mess into Canon Discontinuity.
Final Crisis (2008): Picking up at the end of the year-long weekly series Countdown to Final Crisis and a mounting sense of crossover fatigue among fans, it faced an uphill battle, but the strength of its writer and artist (Grant Morrison and J. G. Jones) saw it through to sales success. The newly reincarnated Darkseid accomplishes his goal of ruling the human race as he unleashes the Anti-Life Equation on Earth, plunging Earth into a black hole that threatens to destroy the Multiverse. The heroes save all of existence, but at the high cost of several high profile casualties (including Martian Manhunter and Batman) and lots of dead civilians who died while Darkseid reigned. Served as the final acts of the "Multiverse Trilogy" ("the Final Crisis of the Multiverse") and the "Exploration Trilogy" ("the day that evil won").
Final Crisis itself is a huge crossover dealing with multiple stories. In addition to the event proper, there was Final Crisis: Rogues' Revenge where the Flash's Rogues Gallery reject Libra's invitation to the new Secret Society and kill the murderous speedster Inertia just before the events of Final Crisis begins; Final Crisis: Revelations which takes place during Darkseid's siege of a controlled Earth as seen by the Spectre and the Question; and Final Crisis: Legion of 3 Worlds (taking place after all the previously listed ) which has the titular 3 Legions fighting against Superboy-Prime and a new Time Trapper and his army of villains before being revealed as an older version of Prime, which ultimately lead to Prime returning powerless to his reconstructed Earth (but having to face the sins of his actions while in the Multiverse).
Blackest Night (2009): Following on from the events of the epic Sinestro Corps War storyline that proved to be infinitely more popular than the Countdown event that was happening at the same time, the culmination of a prophecy first mentioned in an Alan Moore penned back-up strip in "Tales of the Green Lantern Corps" back during the 80s. The best way to describe it is as Space OperameetsZombie Apocalypse. As dead super heroes, super villains, and their families and friends are brought back to life by Nekron, the various color corps from Geoff Johns' run on Green Lantern must put aside their differences and fight to protect all life in the universe. While being heavily Green Lantern-centric, it crosses over with the entire DCU. Most books had at least one issue involved with the event.
The whole thing was initially conceived as a Bat Family Crossover in the Green Lantern books, along the lines of Sinestro Corps War. As mentioned, the absolute success of Sinestro Corps War has lead DC to expand it into a full blown crossover. Even a few canceled books were temporary brought "back to life" for one shot issues just to add to this event. It now seems hard to imagine the relatively simple origins of this event given the hugeness it eventually grew to.
Brightest Day (2010): Following up from 'Blackest Night'', this was a year-long event dealing with the newly resurrected characters' attempts to rebuild their lives after being dead, and the quest for the newly created White Light Battery on Earth. In many ways it was more of a Cross Through; the books involved shared a feeling of making a fresh start but each one mostly followed their own story that was only tangentially connected to the main series.
Flashpoint (2011): This is to The Flash what Blackest Night was to Green Lantern. Barry Allen has woken up to find reality changed around him; now he needs to find out what the heck happened? His discovery of the truth behind the altered world quickly leads to a line-wide reboot on a scale not seen since the original Crisis.
The 40 tie-in stories this event had were very well received (many of them brought back beloved characters and status quos that hadn't been seen in years or even decades). The main miniseries was much less popular.
The main effect this event had on the New 52 universe was that the Superman and Lois Lane of the Post Crisis/Pre-Flashpoint Universe immigrated to the New 52 Universe, as seen in Superman: Lois and Clark.
2017 brings us two:
Dark Nights: Metal sees the Justice League comes face to face with a "Dark Multiverse" with the crossover restoring many elements and characters that have been missing since the New 52 began. A suggested name for it by editors was even "Dark Crisis", but Scott Snyder wanted to stick to the metal theme.
Doomsday Clock is the self-contained example, coming off plot threads that have been built up since the DC Rebirth relaunch started, where the DC Universe crosses over with Watchmen. It ended similar to Metal, by bringing back several things rebooted out of existence with the New 52. This trope even gets Played With, as Dr. Manhattan goes on to predict several over the next thousand years such as another Crisis in 2025 involving Time Masters and the creation of an Earth-56, and a "Secret Crisis" in 2030 involving another Intercontinuity Crossover with the Marvel Universe.
Heroes in Crisis (2018), which features Superman, Batman, and Wonder Woman investigating a horrible massacre at a getaway designed to help heroes with PTSD.
2019:
Event Leviathan, a noir-inspired arc featuring Lois Lane seeking the aid of detective-based heroes to investigate the criminal organization of the same name.
And that is but part of the massive DC Year of the Villain storyline which began in May and concluded in 2020, during which the DCU is essentially in a permanent state of Crisis Crossover.
Dark Nights: Death Metal (2020-2021), which bills itself as an "Anti-Crisis". It is essentially a Crisis event in all but name, taking over the entire DCU for months as the Justice League combat the Batman Who Laughs as the multiverse withers and dies after being invaded by the Dark Multiverse. It ended with the long-promised unboot of the DCU, bringing back pretty much everything pre-Flashpoint and post-Crisis, while expanding the DCU to have several multiverses. In terms of sheer scope and ramifications, Death Metal can be compared to Crisis on Infinite Earths.
Dark Crisis on Infinite Earths (2022), the latest crossover in the DCU. As it turns out, the entire Post-Crisis was one big Myth Arc. A dark entity known as the Great Darkness poses such a threat to the omniverse that both the Justice League and the Justice League Incarnate team up to fight against it. Pariah, who was made a refugee after the events of the original Crisissuddenly switches sides, and rebuilt the Antimatter chamber to let the Great Darkness in an attempt to restore his destroyed world. What follows is the entire Justice League being "killed off." Emphasis on the "killed off" part, as the heroes find themselves in paradise worlds created by Pariah to suit each hero's innermost hopes. It's up to Nightwing and the remaining heroes to reunite the Justice League and combat quite possibly the greatest threat to the DC universe. The sheer scope of Dark Crisis eclipses that on Dark Nights and has implications on not just the Post-Crisis multiverse, but the entire omniverse. It follows through with the resurrection of the Pre-Crisis multiverse, and serves as a Grand Finale to the entire Post-Crisis story arc, 35 years in the making.
