Secret Wars (1984) was the first Crisis Crossover. It lasted twelve issues and was meant to promote a toy line, yet still had some impact on the larger Marvel Universe:
She-Hulk joined the Fantastic Four, while the Thing remained behind on Battleworld.
The stage was set for Magneto to lead the X-Men (reinforcing the parallels between him and Charles) in Secret Wars II.
Spider-Man got his black suit, paving the foundation for Venom a few years later.
In Secret Wars II, the Beyonder, the omnipotent being behind Secret Wars, took on human form and wandered around doing stuff, with the heroes making mostly-futile attempts to interfere with him and Mephisto trying to kill him. While very little changed in the Marvel Universe following the event, Secret Wars II is notable as a legal footnote to the Transformers franchise by featuring an Early-Bird Cameo of Marvel Transformers antagonist Circuit Breaker. Marvel editor Bob Budiansky gunned for her to debut in this story so that she would become the copyright of Marvel rather than Transformers owner Hasbro, causing the latter's 2005-2022 comics licensee IDW Publishingno small amount of headaches in reprinting Marvel's Transformers comics in the 2000's.
The 1986 storyline Mutant Massacre involved the mass murder of the underground mutant community known as the Morlocks at the hands of the Marauders, a group of mercenaries loyal to Mr. Sinister. This series mainly affected the X-books and their characters (at the time, Uncanny X-Men, X-Factor and New Mutants) but it also crossed over into Daredevil, The Mighty Thor and, of all places, Power Pack. It may well be the first crossover which required readers to get every book involved if they wanted to have the full story, a template which almost every crisis crossover has followed since.
Fall of the Mutants, in 1987, which was mostly confined to the X-Books; Evolutionary War, in 1988, which made its way through the Marvel summer annuals (includingALF, which Marvel was doing a licensed comic for at the time) and featured the High Evolutionary; 1989's Atlantis Attacks, also running through Marvel's summer annuals for that year to celebrate the Sub-Mariner's 50th anniversary, as heroes fought off an Atlantean invasion; and other X-Book X-Overs like X-Cutioner's Song and X-Tinction Agenda, each of which made significant, if not always lasting, changes to the X-Status-Quo.
In 1989 came the Inferno (1988) crossover, in which demons from Limbo staged an invasion of New York City. The storyline was mainly an X-Book storyline, as Inferno resolved longstanding plotlines involving Jean Grey's doppleganger Madelyne Pryor, the Madelyne/Cyclops/Jean Grey love triangle, and Illyana Rasputin's Apocalypse Maiden, but the effects of the X-Over was felt in just about every Marvel book published at the time, leading to the introduction of a new Avengers roster, the Thing being restored to human formnote this occurred post-Inferno, but was the result of the Human Torch going to his overpowered Nova Flame mode during Inferno and being unable to power down; when Ben was tossed into the machine being used to restore Johnny's normal state, Johnny emerged in full control of his flame, and Ben emerged a normal human, and the Jason Macendale Hobgoblin becoming half-demon (after getting his ass kicked by Harry Osborn, while dressed as Green Goblin).
Late 1989 and Early 1990 brought the Acts of Vengeance. Loki secretly organized a veritable army of supervillains to fight heroes whom they normally don't. Most notable for the storylines that ignored the main plot, where Spider-Man temporarily gets used to his new Captain Universe cosmic powers, the Fantastic Four testify before Congress against the proposed Super Power Registration Act, Psylocke becomes an ninja, and Magneto takes down the Red Skull in a Moment of Awesome.
During 1991-1993, Marvel ran what has since become known as "The Infinity Trilogy"; three X-Overs written by Jim Starlin, involving Thanos, Adam Warlock, Magus, and the Infinity Gems.
1992 saw the Avengers crossover Operation: Galactic Storm, in which the team was drawn into an all-out war between the Kree and Shi'Ar galactic empires. It turns out the whole thing was engineered by the Kree Supreme Intelligence, who manipulated the Shi'Ar into detonating a nega bomb to spur the stalled Kree evolutionary process, at the cost of billions of Kree lives. Led to a split in the Avengers' ranks when an Iron Man-led team killed the Supreme Intelligence in retaliation (though they only destroyed a shell), much to Captain America's dismay.
1993 brought the Marvel world Blood Ties, a sequel to the Fatal AttractionsBat Family Crossover that involved both the Avengers and X-Men teams traveling to Genosha to save Quicksilver's daughter Luna Maximoff from the predations of the mutant extremist Fabian Cortez. This rescue mission was complicated by the arrival of Exodus, the Dragon Ascendant to Magneto since Attractions and a mutant of Superpower Lottery-level power. Heavyweights from both the Avengers and the X-Men clashed with Exodus, and in the climax he fought off the entirety of both teams singlehandedly before being brought down. Due to the Avengers traveling to Genosha without the approval of the UN, this resulted in them being stripped of their charter and their West Coast team being disbanded.
1993 also brought Mys-Tech Wars, a miniseries building on plot threads in the previous year’s Marvel UK titles. The titular Mys-Tech were the Big Bad for many of those books, a group of ancient sorcerers who’d made a bargain with Mephisto, and were finally ready to put their grand plan into action. As well as the UK heroes, the series used the Avengers and X-Men (among others), with many well-known Marvel heroes becoming cannon fodder before the ending hit the reset button. The effects on the Marvel UK line itself were longer lasting.
The Age of Apocalypse crossover ran through the X-Men books in 1995, halting them for five months to tell the story of an Alternate Universe where Legion accidentally kills Professor X before he could found the X-Men, leading to an apocalyptic world where Apocalypse rules everything and Magneto formed the X-Men instead.
The Crossing ran through the Avengers books in 1995 as well. The premise was that Iron Man had been under the mental influence of Kang the Conqueror for years, and had now turned against the Avengers outright; the only way the Avengers could defeat him was to pluck a younger Tony Stark, untouched by Kang, from an alternate timeline, and in the end, "evil" Tony was killed off.
There's also the Onslaught saga in 1996, which was famously hijacked by editorial to set up Avengers and Fantastic Four's continuities being rebooted from scratch outside the Marvel Universe via Heroes Reborn. However, this reboot was short-lived, and the subsequent Heroes Return storyline not only brought everybody back, but undid the events of The Crossing.
2001 brought Maximum Security, in which a whole mess of alien planets get together to keep all the superbeings we keep producing under control; however, instead of completely borrowing DC's plot for Invasion!, they simply designate Earth as a penal colony, drop off the scum of the universe to keep the superheroes busy, and have a ship in orbit keep everyone from leaving. The plot sickens when Ego the Living Planet begins assimilating Earth as his new body. Yet again, it doesn't work out — but the Kree are given a new Voluntary Shapeshifting gimmick... until the next Cosmic Retcon.
The later 2000s brought a whole series of crossovers, collectively tearing down and then rebuilding the superhero community:
First the Bat Family CrossoverAvengers Disassembled, where The Avengers start getting attacked on all sides out of nowhere. It's eventually revealed that the assault came from the Scarlet Witch, whose powers had grown to Reality Warper levels and driven her mad. She's stopped and placed in the care of her family (Magneto and Quicksilver), but the losses are so great that the Avengers disband (though the New Avengers form shortly afterward after a mass supervillain breakout).
Not long after came Secret War in winter 2004-2005. Nick Fury begins to see that more and more D-list villains are hitting the streets with bigger and better tech, far more expensive than their petty crime could ever pay for. Fury realizes that the weapons are coming from Latveria, but the United States has experienced a thawing of relations with the Latverians and the President vetoes his request to attack and put a stop to the armaments. Fury doesn't take no for an answer and gathers the heavy hitters of the Marvel Universe before launching a black ops invasion of Latveria, completes his objectives, then wipes the team's memories to preserve plausible deniability. The cat gets out of the bag when the consequences come home to roost in New York. Fury is forced into hiding until the events of Secret Invasion while Maria Hill ascends to Director of SHIELD.
2005 followed up with House of M, in which Quicksilver manipulates Scarlet Witch to create "a perfect world", which gets over-ridden by Magneto's concept of a "perfect world" being one ruled by mutants. After much fighting, Scarlet Witch comes to the decision that mutantkind still would create a world of violence and hate, and she promptly depowers 90% of the mutant community. At a stroke, mutant-kind is reduced from a population of millions with strong political and economic support to less than 200 frightened heroes on the verge of extinction.
Civil War, in 2006. The deaths of the New Warriors and the city of Stamford, Connecticut at the hands of Nitro leads to a backlash against all heroes and a political push to get heroes to register their secret identities with the US Government, via the Superhuman Registration Act. Iron Man and Mr. Fantastic decide to back the new law and lead the charge to do so, while Captain America leads the anti-registration side of the super-hero community, as he sees the whole Registration Act as a bad idea. Needless to say, it all ends in horror as Captain America is defeated, denounced as unpatriotic, and assassinated, and Iron Man being handed full-control over SHIELD.
This is followed by World War Hulk, the follow-up to The Incredible Hulk storyline Planet Hulk where, days before Civil War happened, Iron Man, Doctor Strange, Black Bolt and Mr. Fantastic voted to shoot Hulk into outer space. He ended up crash-landing on the hellish gladiatorial world of Sakaar, where he eventually led a revolution, overthrown the tyrannical Red King, and became the planet’s new ruler, at last finding happiness… and then the ship Hulk was sent on blew up, killing a good chunk of the population including his queen and unborn child. Needless to say, Hulk got pissed and fans get five issues of Hulk delivering karmic beatdowns towards Iron Man, Mr. Fantastic, and just about anyone else who gets in his way, as well as crossover issues in or with The Avengers, Ghost Rider, Heroes for Hire, Iron Man, Ant-Man, The Punisher, and the X-Men, not to mention a Prologue issue with a story that features the Mini Marvels filling in the background.
Secret Invasion, in 2008. After the ninja assassin Elektra is killed (again), the Avengers discover that "Elektra" was actually an alien Skrull impostor pretending to be Elektra. Both characters and fans quickly started wondering who else could be a fake, fueled by Word of God explaining that the infiltration went back for years. On top of all the problems from the last few Crisis Crossovers (Captain America dead, the Avengers fractured and preoccupied with fighting each other rather than actual threats, and the X-Men have had their power drastically reduced), throw in the paranoia of double agents and it sure would be trouble if the aliens decided to invade now that every force that could be expected to stand up to them has been crippled... Ultimately, while Earth wins, Iron Man is still blamed for FUBARing the superhuman response, S.H.I.E.L.D. is dissolved, and control of the rest is handed over to the media darling who killed the Skrull queen on live TV; the leader of the Boxed Crook team the Thunderbolts: Norman Osborn.
Finally in 2010, we have Siege. Thor had previously moved Asgard to Earth, and Osborn and Loki aren't happy (Osborn because it's foreign territory on US soil, Loki because Asgard isn't in its own realm where it belongs). So Loki convinces Osborn to lead the Dark Avengers in a massive attack against the Asgardians, with almost every hero joining forces with Thor to repel the invasion. The crisis reaches its climax when the Sentry, immeasurably powerful and mentally unstable superhuman, breaks free from Osborn's control and threatens to destroy the Earth. In the end, Osborn is ousted and the resurrected Steve Rogers (no longer Captain America) takes his place, beginning "The Heroic Age" by ending Superhuman Registration, formally reuniting the fractured Avengers teams, and bringing the Big Three (himself, Thor, and Iron Man) together on the same side for the first time since before Avengers Disassembled.
Starting in 2006, Marvel released Crisis Crossovers for its cosmic properties (i.e. alien races and space-borne heroes who can't be expected to care about the political squabbles on Earth):
The first one came in 2006 during the Civil War, titled Annihilation. It featured Annihilus, ruler of the Negative Zone, making a grand and destructive invasion into the regular universe that left a great deal of heroes dead, utterly destroyed the Nova Corps, dealt a harsh blow to the Kree Empire, and utterly shattered the Skrull Empire, going so far as to destroy the Skrull homeworld (which motivated the Skrull race to activate their sleeper cells to conquer Earth as a new homeworld, leading to the events of Secret Invasion). Ronan the Accuser was forced to Mercy Kill the Kree Supreme Intelligence to temporarily stave off the collapse of their empire. It took the power of Galactus himself, in an all-consuming rage, to end the threat of Annihilus.
Annihilation got a sequel in 2007 titled Annihilation: Conquest, in which Ultron, leading a vast army of robot warriors, takes advantage of the weakened and confused state of the Kree Empire to attempt to conquer it. He doesn't succeed, but he makes a very good try of it and drives the Kree further into isolation and general impotence.
While not directly related, this is followed in 2009 by War of Kings. Part-way spun out from Secret Invasion, one of the people replaced by a Skrull was Black Bolt, leader of the Inhumans. In response, the Inhumans decide they can't live in hiding any more, so their giant city on the moon blasts off for outer space, and after picking off several leftover Skrulls they conquer the remains of the Kree Empire, who created them in the first place. This sets up a war between the Kree Empire and the Shi'ar Empire, itself now under the heel of the psychopathic X-Men villain Vulcan, with the Nova Corps, the Starjammers and the Guardians of the Galaxy caught in the middle.
2010 finishes with The Thanos Imperative. A superweapon detonated at the end of the war has opened a rift in space known as the Fault. On the other side is a parallel universe that has been taken over by Eldritch Abominations (called the "Cancerverse", after how the monsters spread and corrupt). The heroes will have to join forces with Thanos, who had been granted the death he wished in Annihilation and was resurrected against his will in order to fight a universe where life has won over death.
The New 10's brought a regular rotation of Crossovers, often coinciding with promotions for Marvel movies:
Starting in 2010 and continuing into 2012, Avengers: The Children's Crusade brought the Young Avengers, the Avengers, and the X-Men together to hunt down Wanda Maximoff. The Young Avengers sought to return her to the Marvel Universe, the Avengers generally wanted to contain her power, and the X-Men were out for blood after the Mutant Decimation. Wanda was found and all was forgiven after a long The Reason You Suck speech pointing out the hypocrisy of the Avengers and X-Men. Other important events being Victor von Doom revealing he was responsible for Wanda's descent into madness, Iron Lad undergoing his Face–Heel Turn into Kang the Conqueror, Stature dying at the hands of Victor von Doom and spurring said Heel Turn, and Hulkling proposing to his boyfriend Wiccan.
The big crossover of 2011 was Fear Itself. While the world is in a state of underlying fear and paranoia (from events both in-universe and in the real world), the Red Skull (II aka Sin, daughter of the original) frees a Norse god that scares even Odin called the Serpent. The Serpent then summons hammers that turn selected superhumans into his followers "the Worthy", causing the powder keg of fear to explode among the people.
2011 had a smaller example in the form of Spider-Island which saw everyone in New York receive spider powers. While this would normally be a Bat Family Crossover or just a regular storyline in Amazing Spider-Man, a multitude of tie in mini series and one shots focusing on everyone from the Avengers to the Kung Fu heroes as well as tie-in issues running in the monthly titles of both Venom and The Incredible Hercules.
2012 brought Avengers vs. X-Men, where the Phoenix Force is returning to Earth and has chosen Hope Summers as its new avatar, leading the two major Super Teams of the Marvel Universe to clash over whether this will mean the resurgence of mutantkind (for the X-Men) or the destruction of humans and mutants alike (for the Avengers). Epic Conflict Ball ensues. The series ended with Cyclops, Emma Frost, Magik and Colossus becoming fugitives, Professor X dead at Cyclops' hands, and Captain America formed the Avengers Unity Squad to keep something like AVX from ever happening again.
Spring of 2013 brought Age of Ultron, resurrecting Ultron after his cosmic hijinks and the end of humanity with it. Interestingly, the storyline already starts off with Ultron succeeding in taking over the Earth, with the surviving heroes attempting to mount a resistance to stop the robotic villain's rule. Then it quickly turns into Timey-Wimey Ball nuttiness with no real impact on the other titles. Any tie-ins in other books were labeled "AU", and had no impact on their respective running storylines. The major impact came at the end of the story, with the debut of Angela, and Galactus being teleported to the Ultimate Marvel universe, setting the stage for Cataclysm: The Ultimates' Last Stand.
Meanwhile, Summer in 2013 brought Infinity. Building off a storyline from The Avengers main book, it centers around heroes dealing with two major cosmic threats, one a new cosmic enemy called the Builders and the other Thanos leading a new invasion army, hitting the planet Earth at nearly the same time. Despite the name and use of Thanos, Word of God says that the event is not intended to be a sequel to the similarly named The Infinity Gauntlet and its sequels.
2014 kicked off with Original Sin by Jason Aaron and Mike Deodato Jr. It is a murder mystery about the killing of Uatu the Watcher and the heroes' buried secrets which he has personally witnessed but kept to himself being leaked out to the superhero community. (It's highly reminiscent of DC's Identity Crisis (2004).) The culprit was exiled to the moon, forced to watch the Earth as Uatu once did for their troubles.
Fall of 2014 brought AXIS by Rick Remender. Spinning out of the events of Uncanny Avengers, the threat of the Red Skull takes on new heights as his new powers begin to turning the lives of The Avengers, the X-Men and even several noteworthy Marvel villains upside down in his bid for domination. Cassie Lang and Brother Voodoo are returned to the world of the living during this event.
In 2015 there was only one headline event: a new Secret Wars by Jonathan Hickman, where the entire Marvel Multiverse was destroyed and a new Battleworld created from their shards. An "All-New" universe took the place of the old one after the series ended. Ultimate Marvel fan favorites like Miles Morales were merged into the primary Marvel Universe while the rest of the Ultimate Universe was completely destroyed.
In early 2016, Avengers Standoff was launched and the Marvel heroes discovered a S.H.I.E.L.D. facility that used a living Cosmic Cube named Kobik to rehabilitate super villains. Rehabilitation in this case is a polite way to say "brainwash into living peacefully in a false suburbia prison." The prisoners woke up to go on a Roaring Rampage of Revenge while the heroes tried to contain the damage. The fallout from Standoff left most of the Marvel U with a heavy distaste for S.H.I.E.L.D. and central authority in general, and Steve Rogers is mind-wiped into being a sleeper Hydra Agent.
Next in 2016 we had Civil War II in which the superhero community was split in half again, this time over a Precrime Arrest moral debate when an Inhuman named Ulysses begins suffering accurate visions that make Nostradamus look like an amateur, and Inhumans vs. X-Men in which the Inhumans fight the X-Men. Carol Danvers leads the pro-Precrime faction with the Inhumans while Tony Stark leads the anti-Precrime faction. Ultimately, Tony was left in a coma and Riri Williams assumed his mantle as Ironheart, Carol Danvers was able to institute more powers and reforms for herself and S.H.I.E.L.D., a global space shield was erected to protect Earth from cosmic threats, and the Inhuman Ulysses ascends to join the Watchers and remove his prophecy powers from the material world. Which comes in handy for Cap's plans in...
Secret Empire by Nick Spencer was 2017's primary Crossover, in which the Steve Rogers Captain America, who has become an agent of Hydra unbeknownst to the rest of the Marvel Universe, has taken over as head of S.H.I.E.L.D. as he begins his putting his bigger plan of taking over the country into motion, forcing the rest of the Marvel Heroes to band together to stop him. Carol Danvers was locked out of the Earth by her own space shield and the Cosmic Heroes (along with anyone who had a shot at kicking Hydra Cap's ass) was forced to fight an endless armada of Chitauri in space until the war's end. Hydra Cap was ultimately stopped and normal-Cap remade from the shards of the Cosmic Cube.
A smaller Crisis Crossover took place with Monsters Unleashed, a mini-series that forced the heroes of the world to band together against a seemingly never-ending onslaught of colossal monsters from space known as Leviathons. It also serves as the Origin Story for Kei Kawade, who later takes up the hero name of "Kid Kaiju".
2018 had Infinity Countdown leading to Infinity Wars (2018), where the the Infinity Stones reappeared and Doctor Strange gathered up the Stone holders in preparation against a mysterious being known as Requiem, who seeks the Stones.
2019 debuted War of the Realms, Malekith and his army, having taken nine of the Ten Realms, now comes for the final realm: Earth. Thor must now prepare everyone in defense of Earth and the war to come. After the dust settled, Odin abdicates as King of Asgard in favor of Thor, Jane Foster joins the Valkyries as the Valkyrie, and Loki begins to establish a realm of his own among the Frost Giants.
The roaring 20's initially sought to shrink down the cast of crossovers from "everyone gets involved" to "select large groups" get involved.
2020's crossover event was Empyre. Hulkling embraced his dual royal bloodlines and leads a unified Kree-Skrull Empire to war against the Cotati, a plant-like species preparing to launch a genocidal crusade against all "animals" in the galaxy. During the event, Hulkling becomes a true Emperor instead of his initial status as a figurehead, the Kree/Skrull War comes to an end under his rule, the Cotati are exiled to a garden world in an unknown region of space with no power to pursue vengeance, and Abigail Brand falls out with Captain Marvel over her running of Alpha Flight and failure to consult with the team about policy regarding the Cotati at the very beginning of the war. Also, Hulkling and Wiccan finally get married.
2021 brought two major events. King in Black saw Marvel's earthbound heroes team up against the symbiote god Knull. Major fallout includes Eddie Brock becoming the new god of the Symbiotes, a mass death of vampires who came out to prowl after the mass symbiote membrane around the sky was lifted, and Mayor Wilson Fisk forming a new team of Thunderbolts.
The major crossover of 2022 was Judgment Day (Marvel Comics), as the Eternals went to war with the mutants of Krakoa for being Deviants, with the Avengers caught in the crossfire. When the dead celestial of Avengers Mountain was reawakened to try and stop the Eternals' "programming", all sides discover to their horror that the new god The Progenitor takes no sides, and will instead judge every person on Earth by its own standards. If more people are found lacking than not, then it will destroy the Earth and everyone on it. Major fallouts included a mutant genocide on Mars thanks to the Eternal Uranos being unleashed by Druig, the death of Magneto (who never made a "backup" of his personality that would allow resurrection by The Five of Krakoa), the Eternals' secret that a human dies to resurrect them is exposed and they suffer similar hatred given to mutants for it, Krakoa opens up resurrection to normal humans through the Phoenix Foundation, and the anti-Mutant group Orchis sees a surge of support after they joined the battle against the Progenitor.
Marvel's first major event of 2024 will be Blood Hunt, which will see the Avengers, Doctor Strange, and Moon Knight attempting to stop a Vampiric global uprising.
In the same vein, the Marvel Ultimate Alliance video game has the heroes banding together to stop villains under Dr. Doom and Loki from pulling off an Evil Planthat would allow Doom to steal the power of a god from Odin. The sequel is an adaptation of the Secret War and Civil War, minus the second half of Civil War as the game diverges at the end of the third issue of that storyline for a different, original ending where the heroes must band together to stop one of Mr. Fantastic's pro-reg scientific plans gone out of control from dooming humanity's freedom.
Ultimate Marvel had one with Ultimatum, meant to be the last title in the Ultimate Universe before it got relaunched as Ultimate Comics in 2009. The plot involves Magneto plotting revenge on the Ultimates for the murder of the Scarlet Witch, killing absolutely everybody in the process.
In 2011, Ultimate Marvel had The Death of Spider-Man where, well, Spider-Man died. It ran through Ultimate Spider-Man and Avengers vs. New Ultimates, but is something of an odd case as thus far the series have only intersected once (Spidey got injured in an Avengers/Ultimates fight) and have since remained separate, but it serves as an explanation as to why Spider-Man has to fight the Sinister Six with no back-up beyond an ill-prepared Iceman and Human Torch. Nonetheless, it prompted a second linewide relaunch.
In 2012, Ultimate Marvel had Divided We Fall/United We Stand which involved all three ongoing titles at the time - Ultimate Comics Spider-Man, Ultimates and X-Men - dealing with a fractured United States. It notably culminated with Captain America being voted in as President of the United States.
In 2013, the Ultimate line had Cataclysm: The Ultimates' Last Stand, which deals with the aftermath of Age Of Ultron with the Ultimate heroes banding together to fight off Galactus.
