Crossovers are a staple of comic book super-heroism, ranging from battles for the fate of the multiverse to smaller, more personal battles centered on a particular character or group. Marvel has had its fair share of title-spanning team-ups over the years, ranging from the critically beloved stories to those better left in the bargain bin.
The particular reception a story earns doesn't always dictate whether that story will make an enormous impact. Some stories, like the seminal Kraven's Last Hunt, changes little more (in-universe) than the relative position of Spider-Man to one of his villains. For every quiet crossover, however, there are ten that promise the All-New, All-Different.
10 Avengers: Disassembled Began A Decade Of Events
Following a highly praised stint on Daredevil, writer Brian Michael Bendis became one of the critical Marvel architects of the 00s and 2010s. This tenure kick-started with the controversial Avengers: Disassembled, a story that ended the book's classic numbering and brought an end to Earth's Mightiest Heroes.
Disassembled was brutal for classic fans, who watched the Scarlet Witch kill characters like Hawkeye, Thor, the Vision, and Ant-Man in a turn of villainy that became character-defining. The Avengers ended, but in its place grew New Avengers, a book that made characters like Luke Cage, Spider-Man, and Wolverine crucial to the team.
9 Civil War Destroyed The Hero Community
Marvel's Civil War is a storyline crucial to the company. Not only did it provide the basis for critical MCU film Captain America: Civil War, it also set the stage for much of the later 00s/early 2010s, driving a wedge between two of the greatest Avengers.
Besides implementing the Superhero Registration Act, Civil War made plenty of smaller critical changes: Iron Man became the Director of S.H.I.E.L.D., Captain America was assassinated, and the New Avengers went underground. If Disassembled is the storyline that broke the Avengers, Civil War completely shattered them.
8 House Of M Rewrote Mutancy For A Decade
Spinning directly from the events of Avengers: Disassembled, House of M saw the Scarlet Witch rewrite the entire Marvel Universe. In the new reality, Magneto ruled the now-mutant-dominated world as patriarch over the eponymous House of M. This paradigm created a series shift in nearly every major Marvel character's backstory.
While most characters in this reality saw their dreams fulfilled (Spider-Man was married, Quicksilver and his family got along), losing their greatest desires when the crisis ended brought these characters great anguish. However, the biggest change this event caused was the depowering of nearly every mutant on the planet, something that would last until the 2010s.
7 The Original Secret Wars Defined The Marvel Crossover
While Contest of Champions and The Avengers/Defenders War came first, the original Secret Wars became the crossover that really started it all. Originally created to sell toys, writer Jim Shooter and artists Bob Layton and Mike Zeck made Secret Wars more than a cynical cash grab.
A series that featured many of Marvel's most classic characters meeting and beating each other, Secret Wars created some massive continuity waves. Spider-Man gained his iconic black suit (leading to Venom's introduction), the Thing left the Fantastic Four, and it marked Magneto's first portrayal as a heroic figure.
6 The Second Secret Wars Exploded the Multiverse
The second event titled Secret Wars saw every existing Marvel reality combined into one Battleworld ruled by a despotic Doctor Doom. The series from 2015 literally rewrote the Marvel multiverse, and architect Jonathan Hickman wrapped up decades-long plotlines in his massive masterwork.
While the event featured dozens of incredible moments and miniseries, the true impact of the event was felt in the multiverse's destruction, ending critical timelines like the Ultimate Universe. The series also saw the disappearance of the Fantastic Four from mainstream continuity and launched the rise of the Inhumans.
5 Onslaught Led To Disaster For Earth's Heroes
Classic 90s event Onslaught became one of comics' most infamous crossovers, and with good reason. When event architect Scott Lobdell began planting its seeds, he didn't even know what Onslaught was. One murderous, psychic Voltron later, Marvel's heroes and Doctor Doom were embroiled in battle against the manifestation of Magneto and Charles Xavier's evil.
Onslaught had a wide variety of effects. It concluded the "X-Traitor" plotline, something that caused the time-travelling Bishop to question his place in the then-present. However, the biggest consequence was the apparent death of the Avengers and Fantastic Four. Their disappearance started a massive wave of anti-mutant action and the Heroes Reborn imprint/crossover.
4 Dark Reign Began Rekindled 2000s Marvel
Somewhere between an event and a status quo, Dark Reign bled into nearly every Marvel title from 2008 to 2009. Following Secret Invasion, Norman Osborn became the prime mover in the MU, creating the Dark Avengers, battling the X-Men, and enforcing his tyrannical will on Marvel's capes and civilians alike.
While Dark Reign led to things like the Punisher's death and the further isolation of the mutant community, it also helped the hero community reunite. Regardless of things like registration status, heroes trusted each other again and reformed bonds of trust.
3 Original Sin Illuminated The Underbelly Of The Marvel Universe
While 2014's Original Sin event often gets overlooked by many perusing Marvel's list of mega-events, it's a critical chapter in many characters' books. Following the shocking murder of the Silver Age staple Uatu the Watcher, the heroes of the Marvel Universe seek to uncover the killer.
In their hunt, dozens of secrets were unearthed, such as Iron Man's true parentage and the truth behind S.H.I.E.L.D. mainstays Dum Dum Dugan and the original Nick Fury. Other characters, such as Angela and Silk, saw their debuts in tie-ins while Thor became unworthy of Mjolnir. Of course, the most shocking development may be that J. Jonah Jameson was a fan of Spider-Man as a wrestler.
2 The Mutant Massacre Was The First X-Event
Secret Wars may have been the crossover that canonized the concept, but Chris Claremont and Louise Simonson's Mutant Massacre became the first that tied together a series of ongoing books. While the mutant-hunting Marauders laid waste to the outcast Morlocks, the X-Men, Thor, Daredevil, and even the Power Pack sought to stem the bleeding.
While the biggest meta-textual impact of the Mutant Massacre was the creation of annual X-events, there were plenty of in-universe consequences. Nightcrawler, Angel, and Shadowcat received incapacitating injuries, and Wolverine learned Jean Grey was alive again. Fan-favorite book Excalibur launched out of this crossover as well.
1 World War Hulk Shattered The Illuminati
Set against the events of Civil War, World War Hulk saw the Earth-exiled Hulk return from his gladiatorial conquest of the planet Sakaar. Now with his brethren-in-arms the Warbound, Hulk sought revenge on the members of the Illuminati for his treatment at their hands.
After thoroughly beating the majority of the heroes of Earth, Hulk had the members of the Illuminati battle each other in Madison Square Garden. Because of this event, the Illuminati's existence was revealed and the hero community was further fractured. As for Hulk, he returned to Earth, and the foundation was laid for Red Hulk's creation.