There are more than a few marquee characters in Marvel Comics, but the biggest subgroup are mutants. Various forces want to subjugate mutants, if not outright destroy them. Thankfully, the X-Men are there to defend them against any and all threats coming their way.
Since the original X-Men roster first appeared in 1963, there have been several huge stories that have changed the game for mutants as well as Marvel Comics as a whole. While there are hundreds of stories across thousands of comics, there are more than a few that stand out as the most important in the history of the comics.
10 "X-Men: Proteus" Introduced A Powerful Villain & Set The Stage For Dark Phoenix
The son of X-Men ally Moira MacTaggert, Kevin MacTaggert was a mutant born with the ability to warp realities at a whim. But the side effect of this extreme level of power was that it burned out his body, forcing him to look for new hosts. It got the point that Moira had to imprison him to protect other people.
Facing off against Proteus not only brought in one of the X-Men's most dangerous villains in an epic battle, it set the stage for the arrival of the Dark Phoenix. Being that Proteus was an energy being, he always has the potential to reappear and menace the world again.
9 "The Brood Saga" Unleashed The Powerful Alien Race
One of the worst forces in the universe are the Brood. They are a race of alien monsters that exist solely to procreate, which they do by infecting and mutating their victims. On top of that, they are powerful warriors who can overwhelm their enemies with their vast numbers.
"The Brood Saga" cemented these creatures as a key force of evil in the galaxy. They have been part of several stories since their first big one, and have faced off with heroes from outside of the X-Men's immediate circle of characters.
8 "Age Of Apocalypse" Saw Legion Accidentally Murder Professor X & Apocalypse Take Over The World
Legion had a lot of issues. The son of Professor X had multiple personalities, each one of which had its own distinct mutant ability. Trying to help his father, Legion travelled back in time to kill Magneto before he betrayed Professor X. Unfortunately, Legion screwed up and killed his own father.
Without Professor X to stop him, a new timeline was created where Apocalypse became ruler of the world. Magneto and his band of mutants fought back. After the timeline was reset, several characters made the leap to the main continuity and became key players in various stories.
7 "X-Tinction Agenda" Was The Undoing Of Genosha As A Slave System
Genosha has gone through a lot of changes throughout its existence in Marvel Comics. In the late 1980s and early 1990s, it was best known as a small island nation that was built on the backs of mutant slaves who had been brainwashed.
In "X-Tinction Agenda," the X-Men and their allies were forced into confronting and destroying this system. Their old enemy Cameron Hodge was using Genosha to destroy the X-Men. Ultimately, he was destroyed by them instead. The event saw huge changes for Wolfsbane and Havoc, as well as the death of the character Warlock.
6 "The Fall Of The Mutants" Had Repercussions For The X-Men, X-Factor, & The New Mutants
What made "The Fall of the Mutants" interesting was that it was comprised of stories running through three different mutant titles. But they never crossed over, instead telling different stories that changed up the status quo of each team.
The New Mutants suffered through the death of their teammate, Cypher. They also essentially fired Magneto as their headmaster. The events that happened in Uncanny X-Men also led to Storm regaining her lost powers and the X-Men being put in the position where the world thought they were dead for a time.
5 "E Is For Extinction" Saw The Destruction Of Genosha & Introduced Secondary Mutations
Grant Morrison is one of comics' most respected storytellers, and "E is for Extinction"— where he teamed with illustrator Frank Quitley— certainly shows off why. It was an epic story that saw the destruction of Genosha, which was at that point essentially a mutant paradise. After the Sentinel attack, it was a mutant graveyard.
The story also pulled off a stunt that Doctor Octopus would later use on Peter Parker. Cassandra Nova switched bodies with Professor X, then shot him in her body. It also introduced the concept of mutants having secondary mutations, specifically Emma Frost's diamond form.
4 "House Of M" Showcased Just How Powerful Scarlet Witch Truly Is
After the events of "Avengers Disassembled," Scarlet Witch was contained on the devastated island of Genosha by Professor X and Magneto. The Avengers, X-Men, and other heroes decided to kill Scarlet Witch before her powers destroyed the world. But before they could, Quicksilver coerced his sister into creating an alternate reality.
In that world, mutants were in charge, but everything got put back to normal eventually. Almost. As part of the process, Scarlet Witch brought Hawkeye back to life, depowered the vast majority of mutants, and all of Wolverine's memories were returned. It was yet another example of her extreme levels of power.
3 "Mutant Massacre" Was A Bloodbath For The Morlocks & Saw Angel Transition Into Archangel
This was one of the most horrifying events in the history of the X-Men. Led by Sabretooth, the Marauders attacked the Morlocks, a group of mutants living under New York. They slaughtered hundreds of Morlocks before the X-Men, X-Factor, Power Pack, and Thor all intervened.
The losses inflicted were heavy, and continued to influence future stories. A huge change during the event was the crucifixion of Angel. His wings were ultimately amputated, setting up his transition into Archangel. The involvement of Mister Sinister, Dark Beast, and Gambit also continued to have repercussions.
2 "Days Of Future Past" Set New Standards For Time Travel Stories In Comics
This arc may have only been two issues of The Uncanny X-Men in 1981 but its impact continues to reverberate in comics today. The story involved a future version of Kitty Pryde transferring her consciousness into the past version of herself. Her goal was to prevent something awful from happening.
The dystopian future shown in the story changed how the X-Men approached their mission. Other stories would return to the timeline, but the biggest change was Rachael Summers. The daughter of Scott Summers and Jean Grey from that timeline, she joined the main continuity and became a prominent character.
1 "The Dark Phoenix Saga" Is One Of The Greatest Comic Stories Of All Time
This story is widely considered to not only be the best X-Men story of all time but also one of the best comic book stories in general. The arc of Jean Grey realizing her full power, then sacrificing herself to protect everyone she cares about, was brilliantly executed.
"The Dark Phoenix Saga" has also become a cornerstone of Marvel storytelling. The impact of that arc can be seen in various characters, particularly Scott Summers and Jean Grey. The Phoenix Force also continues to be an ongoing factor in Marvel Comics, effecting a number of characters.