The greatest advocate for mutant-kind that has ever lived, and an uncompromising pacifist, Professor Xavier was a beacon of hope for mutants and humans alike, dedicating his life to their peaceful coexistence. On the surface, he seemed to be a saint, accepting mutants from all walks of life, regardless of their past or powers. Yet those who worked alongside him - especially his students and closest allies - found him to be secretive and manipulative, often using his powers to remove all evidence of his wrongdoing.

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Add to that his shady family history and Professor X, created by Stan Lee and Jack Kirby, falls far short of being the mutant equivalent of Martin Luther King Jr. whom we had hoped for. In fact, Charles Xavier has his fair share of skeletons in his closet, and these are his 15 darkest secrets.

15 HIS MURDEROUS ANCESTOR

Xavier's Murderous Ancestor

Let's start off with his psychopathic family, which could be one of the most rotten families in the entire marvel universe. How do we know this? Well in "X-Men: Manifest Destiny" #3, by Marc Guggenheim and artist Yanick Paquette, we're introduced to a strange looking mutant who has arisen from the remains of the Xavier Institute after a sentinel attack. Beast's analysis confirms that he's over 200 years old and that his mutant powers have kept him alive all this time. As he recounts his tragic origin to Anole, we find out that his name is Jonas Graymalkin and that he was born in the late 18th century to Charles and Marcia Graymalkin.

At the age of 16, he discovered that he was gay, but unfortunately so did his father, who like most men at the time, didn't have much tolerance for homosexuals. Ashamed and infuriated, his father severely beat him and then buried him alive after finding him in the family barn with a local boy. Beast's analysis also confirms that he was Xavier's ancestor, who likely received his namesake from his murderous ancestor. A dark start for the Xavier family!

14 HIS FATHER WORKED WITH MR. SINISTER

Xaviers Father Worked With Sinister

Xavier was not only one of the most powerful telepaths to have ever existed, he was also one of the smartest men alive, possessing a genius-level intellect. An intellect that he probably inherited from his father, Brian Xavier, who earned a considerable fortune as a nuclear scientist and left Charles a sizeable inheritance, which he used to found his school for gifted youngsters. But did you know that this fortune was acquired by questionable means?

Piecing together information from "X-Men Forever" #4 and "New X-Men" #41, we discover that in 1946, Dr. Xavier joined an very suspicious-sounding government project called Black Womb. A project that studied thousands of mutant babies and held them in tanks. Some of Brian's colleagues included the twisted Dr. Alexander Ryking, Dr. Kurt Marko (see below) and Dr. Nathan Milbury (a.k.a. Nathaniel Essex), who would become the evil geneticist Mr. Sinister. Created by Stan Lee, Jack Kirby and Alex Toth, Brian Xavier perished in the explosion that destroyed the project's facility in New Mexico, leaving Charles to grow up without a father.

13 HIS SCHEMING STEP-DAD

Xavier Stepfather

After Brian perished in the explosion, his colleague Kurt Marko (created by the same team mentioned above) was quick to pick up the pieces, providing a shoulder for Sharon Xavier to cry on and a body to warm her at night. In "X-Men" #12, we read that even at Brian's funeral, Kurt was working his way into Sharon's heart, persuading her that she needed his help. As a child Charles immediately sensed Kurt's less than noble intentions, knowing that he's only interested in his mother's money.

Sharon Xavier dies shortly afterwards, having been driven to alcoholism by her negligent new husband who is often away and physically abusive to his own son Cain Marko, a.k.a. the Juggernaut. No wonder he became a creature of pure hate! Towards the end of the issue, young Cain accidentally causes a lab explosion and, in his only unselfish act, Kurt saves the two boys, but not before revealing that he could have saved Brian Xavier but chose to let him die instead.

12 HE TRIED TO KILL HIS UNBORN TWIN

Baby Xavier attacking baby Cassandra Nova

While still happily married to Brian Xavier, Sharon became pregnant with twins, one of whom was Charles Xavier, who inherited the family fortune and estate. The other twin wasn't so fortunate. In what is perhaps one of his most disturbing acts, Charles attempted to drive his sister out of the womb with his mutant abilities after sensing that she was evil ("New X-Men" #121). Sharon had a miscarriage and baby Cassandra was pronounced stillborn ("X-Men: Messiah Complex - Mutant Files" #1) and the doctors discarded her body immediately afterwards.

Unwilling to die, Cassandra spent the next few decades as a mass of cells growing in the sewers, slowly building a new body for herself and planning her revenge on Charles, which she achieved in "New X-Men" #115 when she used wild Sentinels to destroy Genosha, killing 16 million mutants in the biggest genocide the marvel universe has ever seen. Professor X kept this secret hidden for decades and perhaps all of this could have been avoided if he had been willing to talk to her first. Cassandra was created by Grant Morrison and Frank Quitely and possesses powers similar to those of Professor X.

11 HE WAS A TERRIBLE FATHER

Legion using his powers

Created by Chris Claremont and Bill Sienkiewicz, David Haller is a mutant who can possess multiple personalities, spontaneously mutate, reconstruct reality in a heartbeat and, as the sole survivor of a terrorist attack as a child, he really needed a father figure growing up. If anyone was qualified to ensure that he didn't become "Legion," it was Professor X. In "Uncanny X-Men" #161 we read how Charles first met his mother Gabrielle Heller at a psychiatric facility for Holocaust survivors in Israel, and how he uses his powers to heal Gabrielle's pain and restore her sanity.

In return Gabrielle became his lover, after which Charles impregnated her and then left, never contacting her again. Charles first finds out about his autistic son in "New Mutants" #26, where he promises to take care of the boy, and although he does briefly recruit him in "New Mutants" #14, it hardly makes up for how absent Xavier was in his life, especially since David's omega-level abilities have caused several catastrophic events, including the "Age of Apocalypse" storyline.

10 HE TRIED TO MIND-CONTROL HIS GIRLFRIEND

Xavier mind controlling his girlfriend

Now we're really going to get into Xavier's dark deeds. Remember how he first lost the use of his legs in "X-Men" #20 after Lucifer dropped a huge stone on him? Well he needed to recover somewhere, so Sage brought him to a hospital in Tibet. Amelia Voght, who first appeared in "Uncanny X-Men" #300 (Scott Lobdell, John Romita Jr), nursed Charles back to health, helping him get over the depression he experienced when he became a paraplegic.

The couple returned to the states together and Amelia moved into the X-Mansion with Charles, who was overjoyed to discover that his new love was also a mutant. Their relationship hit a snag when Amelia began to doubt Charles' plans for peaceful coexistence with humanity and, in "Uncanny X-Men" #309 she decided to leave him. Charles didn't take it so well, attempting to mind-control her into staying, leaving Amelia feeling violated and betrayed; it wasn't long before she joined the Acolytes instead. This was a serious misuse of Xavier's power, and as we'll see below, misusing his powers was second nature for Charles Xavier.

9 HE ERASED ALL MEMORY OF BEAST

Cyclops attacking Beast

Yup, without asking Hank McCoy, Professor X erased all memory of him from the minds of his family and friends, including high school girlfriend Jennifer Nyles, the love of his life. In "Marvel Comics Presents" #85 Hank storms into the X-Mansion demanding an audience with Professor X, after he has discovered that Jennifer no longer remembers him. Despite begging Professor X to restore her memories of him the Professor refuses, telling the young X-Man that she knew too much and that if there was ever a civil war between humanity and mutantkind, it would be better if Hank's family and friends didn't remember him.

Beast tells us in this issue that on some level he always hated the Professor for doing this, especially since it wasn't his decision to make. Aware that something is missing from her soul, Jennifer spends her whole life seeking to unlock her subconscious and gets mixed up with some dangerous cyborgs. Beast eventually finds her in "Marvel Comics Presents" #92, but their reunion is cut short when Guillaume Courage shoots her in the stomach. After seeing her safely to hospital, Beast decides that it's better for them to remain apart. Nice work, Professor!

8 HE LUSTED AFTER JEAN GREY

Xavier fantasizing about Jean Grey

In "Uncanny X-Men" #3, we're treated to a strange inner monologue from Professor Xavier where he describes his forbidden love for Jean Grey. This secret remains hidden for decades until Onslaught reveals it to Jean when he forces her to meet him on the Astral plane. After taking her on a tour of the city, Onslaught offers to reconnect her with the power of the Phoenix Force if she will join him. Jean refuses and so Onslaught leads her into Xavier's mind, promising to reveal something about the Professor that she doesn't know.

This all takes place in "X-Men" #53 (Mark Waid, Andy Kubert) and Jean responds by telling Onslaught that as two of the most powerful telepaths in the world, there's no secret that exists between them. So you can imagine her shock to learn that her father figure and mentor had once believed he was in love with her. Onslaught reveals that instead of dealing with his inappropriate attraction to Jean, Xavier simply locked it away, along with all of his other negative emotions, which is partly what led to Onslaught's creation in the first place.

7 HE REPROGRAMMED WOLVERINE

Xavier talking with Wolverine

Wolverine is already pretty messed up, unable to remember much of his past or where he came from. The scientists on the Weapon X program did a thorough job of brainwashing him in order to make him a living weapon that they could use for any job. In "X-Men Legacy" #217 and "Wolverine: Origins" #29 Wolverine and the Professor are staking out the Hellfire Club, trying to free Daken from Sebastian Shaw and along the way they repeatedly discuss what happened to Wolverine when he first came to the mansion.

Wolverine reveals that he originally came to the X-Mansion programmed to assassinate Xavier, something he nearly succeeded in doing. Professor X then reveals a secret of his own, that instead of helping Wolverine break free from his Weapon X programming he further broke his mind and reprogrammed him for his own purposes, allowing Wolverine to stay because he "needed a weapon". If you were touched by their apparent father-son relationship in "Logan" you'll be disappointed to know that they aren't as close in the comics, and for good reason!

6 HE ENSLAVED THE DANGER ROOM

Astonishing X-Men angry at Xavier

"Astonishing X-Men" #12 describes the Danger Room's desperate attempts to reach out to the X-Men after being enslaved by Professor X for years. Initially just a high-tech obstacle course for the X-Men to train in, it became sentient when the Professor and Forge upgraded it with alien technology from the Shi'ar. Created by Joss Whedon and John Cassaday, the Danger Room renamed itself as Danger and even built itself a body so that it could take corporeal form.

After luring the X-Men into a simulation it traps them and begins exploiting all of their weaknesses in an effort to get their attention. After Danger has been defeated the students pressure Professor X into telling them the truth, which is that Danger actually reached out to him years ago asking for help, but he decided to let his students continue to use her as a training room, for experimental purposes, essentially making Danger into his slave. This really doesn't go down well with the X-Men, especially Cyclops who calls Xavier's act "the oppression of a new life."

5 HE JOINED THE ILLUMINATI

Xavier and the Illuminati

Remember that super-secret group of superheroes who sent Hulk to Skaar and plotted to kill Scarlet Witch? With all his secrets, it's no wonder that Xavier was a core member of their ranks. In fact it was Xavier who called the group together to discuss potentially killing Scarlet Witch after she killed Hawkeye and destroyed Vision, her then husband. To his credit, he wasn't present when the group decided to exile the Hulk, but when the green giant arrives at the X-Mansion in "World War Hulk" Xavier does tell him that he agrees with the Illuminati's decision.

During the events leading up to "Secret Invasion," Professor X leaves after learning that he can no longer trust the other members of the Illuminati. He then screws the X-Men over once again by restricting who he tells about the imminent Skrull invasion, leaving the X-Men caught off guard when they arrive. You can read all about these events in "New Avengers: Illuminati" #5 by Brian Reed, Brian Michael Bendis and Jim Cheung.

4 HIS SECRET AGENTS

Xavier and Mystique

Okay so this one isn't really a dark secret, but it is pretty cool, especially if you're a James Bond fan. Unbeknownst to the X-Men -- who probably wouldn't be pleased to find out about it -- Professor X had a whole group of expendable mutant secret agents working for him, carrying out missions that couldn't be traced back to Xavier or the X-Men. The 2003 miniseries "Mystique" (Dave Cockrum, Chris Claremont) reveals a lot about these missions, including the name of Xavier's top agent, Prudence Leighton, a.k.a. Agent 16.

Prudence unfortunately dies on a mission -- smoked by arms dealer Steinbeck's fire breath -- and the series gets even better when Mystique becomes one of Xavier's agents! The notorious shape shifter gets sent all over the world on various missions for Xavier and the professor even enlists Forge to secretly outfit her with non-lethal weapons. A standout moment in this series is when Xavier impersonates Magneto to save Mystique from being executed by the government, a fate she most certainly deserves!

3 THE XAVIER PROTOCOLS

Xavier Protocols

Okay, back to the dark secrets, and this is one of the biggest! Remember how Bruce Wayne had a contingency plan to take down his Justice League buddies if they turned evil or were mind controlled? Turns out Xavier had one for the X-Men, too. The Xavier Protocols are a set of doomsday plans created by Professor X that detail the best way to kill many powerful mutants, including the X-Men and Xavier himself. They're first mentioned during the "Onslaught" crossover, when Onslaught gains control of several powerful mutants, and are first seen in "Excalibur" #100 in Moira MacTaggert's lab.

Of course, these plans soon fall into the wrong hands and, in "Operation: Zero Tolerance," Bastion, the android mutant-hater, obtains a copy of the protocols and plans to use them against the X-Men. Thankfully, Cable stops saves the day by breaking into the X-Mansion and securing the files before Bastion has a chance to decrypt them. But on the very same day, Cerebro decides that it wants to become autonomous and attempts to destroy the X-Men itself using the Xavier Protocols. Rule number one: don't make evil contingency plans!

2 HE SENT AN X-MEN TEAM TO THEIR DEATHS

Giant-Size X-Men team

The sad truth is that the X-Men we've come to know and love weren't Xavier's first team. In "Giant-Size X-Men" #1, Professor X is recruiting a brand new group of X-Men to rescue his original team of mutants from Krakoa the Living Island. The original team consisted of mutants like Cyclops, Sway, Darwin, Havok and Petra, all young mutants who had been taken in by Moira McTaggert, Charles' former lover and colleague. But unfortunately, with the exception of Cyclops, all of the members of rescue team #1 are killed.

Xavier, being the great guy that he is, wipes Cyclops' memory - who is led to wrongly believe that the island freed him - and assembles a new team of mutants (let's call them rescue team #2), which includes Wolverine, Nightcrawler, Storm, and Colossus. Xavier's crimes finally catch up with him decades later in "Deadly Genesis," which is a retcon of the original events in "Giant-Size X-Men." Xavier earns even more hate from the X-Men, especially Cyclops, because as we're about to find out below, he stole a lot more than just his memories.

1 HE HID VULCAN FROM CYCLOPS

Vulcan and Cyclops meet

Scott Summers has experienced great loss in his superhero career, losing his parents and his brother Alex while still in his childhood. To make matters worse, he had a third brother, Gabriel, who was taken by the Shi'ar before he was even born. Upon reaching adulthood, Gabriel escaped and returned to Earth, only to make a fatal mistake; he joined the X-Men. In "Deadly Genesis" (written by Ed Brubacker), we also find out that upon first meeting Gabriel, Xavier sensed that he was Cyclops' brother but, for some unknown reason refused to tell Cyclops.

Then, just before his apparent death on Krakoa, Gabriel told his brother the truth, only to lose him again soon afterwards. Thankfully, Gabriel survived and returns to exact revenge upon a de-powered Xavier, proclaiming the truth in front of all the X-Men. When Cyclops and the other X-Men discover what happened, Cyclops rightly banishes Xavier from the X-Mansion, knowing that Xavier not only stole the memories of former friends, but also stole his brother, whom he had never known existed. Once again Professor X's misguided attempts to protect his students -- mostly for his own gain -- ultimately caused them more pain.

Got another chilling fact about Professor X? Let us know in the comments!