The X-Men have been staples of the Marvel Comics line since they first appeared in 1963. Hundreds of mutants have come and gone with events and crossover arcs that spotlight all of Marvel's not-so-merry mutants. There have been movies, cartoons, and countless prose books that feature their struggle to protect a world that hates and fears them.

While there are millions of people who have consumed X-Men content, there are some secrets that are hidden far back in the comic continuity. Only the most hardcore fans will truly have uncovered the biggest secrets that the X-Men have to hide.

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10 Every Original X-Man Has Turned Evil

The founding members of the X-Men have historically been viewed as the champions of civil rights and virtue. They spent their childhoods defending humanity and mutants alike while striving to create a more equitable world. Unfortunately, every member of the original X-Men has become their own worst enemy.

Jean Grey is known for her corruption by the Phoenix, and Beast has slowly been descending into a level of abject villainy. He even committed genocide against the people of Terra Verde. Angel acquired a Death Seed and became the monstrous Archangel, eventually taking over for Apocalypse. The Phoenix Force corrupted Cyclops, and he became a mutant terrorist. Even the light-hearted Iceman has been corrupted — freezing the entire world after holding a Death Seed of his own.

9 Emma Frost Tormented Teenagers

Today, readers know Emma Frost for her love for children. She will do whatever she can to protect the next generation of mutants and has committed morally questionable acts solely to defend them. When she was first introduced, however, Emma was far from an anti-hero.

As the Headmistress of the Massachusetts Academy, Emma Frost regularly worked to capture and mentally torment the New Mutants. These were young teenagers, ranging from 13 to 19-year-olds, but Emma showed no remorse when she regularly wiped their minds and forced them to work for her school. She often pit her Hellions against the New Mutants, just so she could gain control of Xavier's mutants. Emma has come a long way, but she was originally a menace to mutant children everywhere.

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8 An Entire Dead X-Men Team

The X-Men have some dark secrets, but a decimated team led by Cyclops' own brother stands out among the rest. Before the Giant-Size X-Men charged to save the original X-Men from Krakoa, there was another team that Xavier sent after his proteges. Unfortunately, their mission wasn't quite so successful.

Vulcan, Petra, Sway, and Darwin were under the protection of Moira MacTaggert, who was interested in helping them reach their full potential. When the X-Men went missing, however, they charged after Krakoa and were swiftly butchered. Professor X showed his true colors by wiping Cyclops' memory, so he would completely forget about his brother. It was a horrific move that showed just how cruel Xavier can be.

7 Magik Tried To Kill The New X-Men

Magik has become a standout member of the X-Men. She has enough support from the mutant community to earn a place on the 2022 Krakoan X-Men team. That outpouring of love hides a dark secret, however. She spent years of her life haunting the next generation of mutants. Pixie, especially, was a target for Magik's devious schemes.

Magik corrupted Pixie's innocent heart and created a Souldagger with Pixie's soul. It was a horrific decision that forced Pixie to experience all the trauma that turned Magik into a warrior. Magik then tormented the rest of Pixie's team to secure a Soulsword of her own. Magik and Pixie eventually came to terms with each other, but it took years of fighting to resolve their hatred.

6 Kitty Pryde Joined The Guardians of The Galaxy

It was a time that Kate Pryde rarely talks about in recent years, but she was once a leading member of the Guardians of the Galaxy. After falling in love with Peter Quill, Kate took to the stars. She even took over Quill's Star-Lord role, while he desperately attempted to bring order to Spartax.

A leading member abandoning the team to explore a romance in space is something that the X-Men rarely advertise. The era lasted for years, but it has scarcely been mentioned since. Additionally, Kate Pryde became a cosmic entity during the Black Vortex event — a secret that the X-Men books haven't explored since.

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5 Rachel Summers Is A Singular Entity

Marvel's multiverse is filled with multi-dimensional heroes who come to Earth-616 seeking glory or protection. At first glance, Rachel Summers was just another one of those heroes. She arrived from Earth-811, looking for a way to change the past so that she could prevent her harrowed future. As the story went on, Rachel quickly evolved into something more.

Throughout her time with Excalibur, Rachel Summers and the team jumped from universe to universe. While they met countless other versions of her teammates, they never met another Rachel. They realized that, as the daughter of the Phoenix, Rachel was unique in the multiverse. Every version of Rachel is actually just Rachel traveling through time, and it's a secret that the X-Men keep close to their chests.

4 There Is A Secret Spy In The X-Men

With the world hating every mention of mutants, the X-Men have few allies. When they find loyal mutants, they cling to them, because the X-Men have to trust each other to survive. Unfortunately, only hardcore fans know that there is a secret spy hiding among the mutants.

Hunt For Wolverine: Adamantium Agenda #4 (created by Tom Taylor, R.B. Silva, Adriano Di Benedetto, Guru-eFX, and Joe Sabino) revealed that one member of the X-Men isn't a mutant. A plant serving as a Trojan horse, this mysterious mutant has seeded themselves deep within the team. It's a plot that has never been resolved, but it could have serious impacts if it ever sees any resolution.

3 Charles Xavier Loved Jean Grey

Professor X is the founder of the X-Men and a beloved face within the franchise. He has spent decades working tirelessly to protect the mutants that he views as his own children. One of those mutants, however, Charles Xavier viewed through a very different light. In X-Men #3 (created by Stan Lee, Jack Kirby, Paul Reinman, and Artie Simek), Xavier revealed his undying love for Jean Grey.

It was an insidious revelation, given that Charles Xavier was Jean Grey's teacher and protector. Having a romantic attraction to Jean felt like a betrayal, especially when Jean later discovered his love. Xavier's feelings are now often intentionally overlooked because it added a horrifically eerie explanation for Xavier's actions as founder of the X-Men.

2 Jean Grey Was Not The Dark Phoenix

Jean Grey is best known for her role in The Dark Phoenix Saga. After being possessed by the Phoenix, an extraordinarily powerful cosmic entity, Jean destroyed a planet and an entire culture. She turned D'bari IV to ash and made herself an enemy of the Shi'ar Empire. When Jean returned to life, it was with the knowledge that she was now and forever the Phoenix.

A secret that the X-Men keep close to the chest, however, is that Jean Grey was never the Phoenix. X-Factor#1 (created by Bob Layton, Jackson Guice, Josef Rubinstein, Petra Scotese, Max Scheele, and Glynis Oliver) revealed that the Phoenix imprisoned Jean beneath Jamaica Bay and took her form. Jean was never involved in the destruction of D'bari IV. It puts Jean's actions in a new light and completely changes the nature of her character. After all, if Jean wasn't the Phoenix, X-Men history is forever changed.

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1 The X-Men Erased A Mutant From Existence

First introduced after the death of Xavier, Matthew Malloy was an Omega-level mutant. With extreme reality-warping powers, Malloy could rip apart the very fabric of the universe with little more than a thought. He had no true control over his powers, and his fits of rage often led to the deaths of powerful X-Men — including Emma Frost, Cyclops, and Magik. There was little chance of stopping him when his resurrection powers meant he could never truly be killed.

Tempus eventually took it upon herself to go back in time and prevent Malloy's birth. She erased Malloy from existence, and the rest of the X-Men came back to life shortly after. This brutal decision underscores just how powerful mutants are. If a threat is too massive, they can just travel back in time to prevent their enemy from ever existing at all. Because the other X-Men never interacted with Malloy in this new reality, only Tempus and hardcore fans remember what really happened.