No more mutants - the final words of Wanda Maximoff before she reshaped the world once again. The actions of the mentally ill Scarlet Witch have had strong and lasting repercussions across the Marvel Universe. Some of these repercussions were obvious and immediate, such as the de-powering of millions of mutants. Others were more subtle and would only be revealed with time. Irregardless, the Marvel Universe found itself in a new age.
M-Day
For the world, the de-powering of the mutants came out of nowhere on November 2nd. The media immediately dubbed this day as ‘M-Day.’ Several accounts confirmed that after a blinding flash of light, millions of mutants simultaneously lost their powers and became human. However, it seems that the de-powering process, much like Wanda’s House of M reality, has had imperfections. Many mutants lost all aspects of their mutation, while others may have lost their powers but retained some physical aspects. Some mutants seemed to only lose part of their powers, though on several occasions this has led to fatal endings as those with deadly powers suddenly lost immunity and succumbed to their own abilities. However, the de-powering did not affect all mutants as a small number of them retained their abilities.
The media and some survivors were quick to label the remaining mutants as the ‘198’ after an early government report on the initial survivors. However, whether this number is symbolic or literal is unknown as there have been conflicting reports on the total number of mutants left. It is agreed upon, however, that 90-95% of the world’s mutants have been de-powered. Worse yet, it seems that no new mutants have been born since M-Day. The media also came up with another term that isn’t what it seems. The term ‘Decimation’ was given to reference the de-powering. However, this was not really a correct term, as the word literally means to select and kill ten percent, while in this case it was the other 90% that suffered.
Those who know of the truth behind the de-powering are few. Originally it was believed that those under the mental protection of Dr. Strange and Emma Frost when the world reverted remember, but it seems that there are three criteria for remembering the House of M: being present during the initial reality warp on Genosha, being woken up by Layla, and being present during the second reality warp on Genosha. With this criterion, those who remember M-Day are Cyclops, Emma Frost, Shadowcat, Wolverine, Luke Cage, Spider-Man, Ms. Marvel, She-Hulk, Dr. Strange, Quicksilver, and Magneto. Layla Miller remembers due to the nature of her powers, and while Tony Stark and Wanda Maximoff should remember, they don’t, the latter because she erased her own memory, but no reason yet as to why Tony doesn’t remember. Later, it was revealed that Hawkeye and Xavier do remember as well.
The Day After
The X-Men did what they could to help the world’s remaining mutants. After a terrorist attack on the European Office, Cyclops chose to close down all X-Corporation branches in the world, and he made the executive decision to open up the grounds of the Xavier Institute as a safe haven for any powered mutants still around that needed some place to go. The X-Men began to round up whoever they could, but Storm decided to remain in Africa for the time being, not only to help the mutants there, but because she felt it was a bad idea for all the remaining mutants to be in one location. Despite their resilience the X-Men found that they had their own to look after as well, as several X-Men and associates were among the de-powered. For their own safety, Scott and Emma decided to send all de-powered students home.
In response to M-Day, the government launched the Office of National Emergency, under the leadership of Valerie Cooper and General Lazer. They initiated Sentinel Squad O*N*E*, a program with a new breed of 
Sentinels that are commandeered by human pilots trained by James Rhodes. With a State of Emergency declared for mutants, O*N*E*, whose operations are overseen also by Colonel Miguel Reyes, arrived at the Xavier Institute and put all its residents, X-Men and refugees, under house arrest for their own protection. The X-Men had little time to dispute the presence of Sentinels when the Sapien League attacked to destroy the remaining mutants, though were quickly defeated. [Decimation: House of M - The Day After, Sentinel Squad O*N*E* #1-5, X-Men (2nd series) #177-179]
Casualties on the Home Front
While doing their best to help the world adjust to the de-powering, the X-Men also had to cope with their own casualties, such as Polaris, but particularly Chamber, who was in a rather dire situation. His de-powering left him with a gaping hole where his upper chest and lower face would have been. Fortunately the X-Men were able to get him medical treatment swiftly, but due to the dangers of being in the Institute they chose to house him in a hospital. [Decimation: House of M - The Day After, Generation M #1]
At the Xavier Institute, the X-Men personally witnessed first-hand the affects of a de-powered mutant population. There having been a student body of approximately 150,
after M-Day the school was left with no more than twenty-seven students: Anole, Blindfold, Bling, Dust, Elixir, Ernst, Gentle, Hellion, Icarus, Hisako Ichiki, Indra, Loa, Match, Mercury, Onyxx, Pixie III, Quill IV, Rockslide, the three Stepford Cuckoos, Surge IV, Trance, Wallflower, Wither, Wolf Cub, as well as X-23, who was brought to the Institute by Wolverine post M-Day. De-powered teacher Dani Moonstar was asked to step down and leave for her own protection, just like the numerous de-powered residents. Emma desperately sought a way to prepare the remaining students for the future. She took them to the Danger Room, where she had them battle each other in an all out brawl with the winners being crowned the New X-Men, the next generation of X-Men. In the end, Hellion, Dust, Rockslide, Mercury, Elixir, Surge, and X-23 made the cut. [New X-Men (2nd series) #20-23]
In Genosha, all efforts to rebuild the island nation came to a grinding halt, as almost about all the island’s mutant residents were de-powered. Meanwhile, Bishop found that his duties in Mutant Town also came to an end. With the few remaining mutants of the district seeking refuge at the Institute, there was no longer a need to regulate a mutant population as there was no mutant population left. Bishop’s partner, Ismael Ortega, was personally affected by the Decimation. His daughter, Chamayra, whose gun shot was healed months ago by a mutant suddenly lost whatever healing was done to her and died from internal gunshot injuries. [Mutopia X #5, Son of M #4-5]
The ‘198’ and the ‘Decimated’
After opening the grounds of the Xavier Institute, the school grounds became flooded with mutant refugees. With part of the mansion damaged in the fight with the Sapien League, the mutant refugees found themselves camping out on the mansion lawn under the house arrest run by the Office of National Emergency. The group was a difficult one to handle, as it consisted of mass murders and psychopaths among former allies, peaceful individuals and victims of mutant crimes. Due to early news reports citing the unverifiable number of mutants left, the refugees called themselves the ‘198’ and began to become disgruntled as they soon realized that they were losing their civil rights. Several fights broke out and deaths began to occur, putting life in a bind for the X-Men who were losing control of the situation. [X-Men: The 198 #1-5]
Life for the remaining mutants was tough and more dangerous than ever, but life for the de-powered was not easy either. 
Journalist Sally Floyd, saw the other side of the mutant crisis and began a series of articles interviewing de-powered mutants and their lives post M-Day. Among her articles was a feature on the hospitalized Chamber, former X-Man Stacy X, as well as the remnants of the Morlocks and the worries of their de-powered leader Marrow. Sally’s Mutant Diaries won her acclaim, though left her as a target of an insane mutant who felt that not enough people died on M-Day. [Generation M #1-5]
The Twins Who Changed the World
After the House of M ended, the Scarlet Witch was among the missing. Emma Frost could not find her with Cerebra, nor could Dr. Strange track her with his magic. Even Magneto and Quicksilver had no clue where she was. With no leads or clues to the whereabouts of Wanda, and having their hands full with the devastation wrought on by her powers, the heroes made finding Wanda a back seat priority. However, Hawkeye wanted to seek her out for closure since she killed and resurrected him – not only once but twice. Hawkeye traveled to Wundagore Mountain and surprisingly found her, but she had no memories of her past, denying him the closure he desired. Apparently Hawkeye has kept her location a secret. [New Avengers #26]
Meanwhile, the man who created this mess, Quicksilver, found himself de-powered and almost penniless in New York City. His grief led to a suicide attempt, but he was found by Crystal who took him to Attilan. There Quicksilver recuperated and came up with the idea to re-power himself with the Terrigen Mists, but had to resort to stealing some of the crystals that emit the Terrigen Mists. He gained the power to travel short distances back in time and even exposed his daughter to the Mists, unlocking her Inhuman potential for superpowers. However, when Pietro decided to flee to Earth to re-power the world’s mutants he was found by the O*N*E*, who confiscated the crystals, causing the Inhumans to declare war on the United States. Quicksilver, however, had kept some crystal fragments and stored them in his own body, giving him the ability to re-power others with varying results. [Son of M #1-6]
Ghosts From the Past
When Wanda re-made the world, the energy that was formerly wielded by mutants had to go somewhere, and in fact it was jettisoned out into space where it collected itself. In Earth’s orbit, the energy had the effect of awakening a dormant mutant named Vulcan, who was lost out there for years. Vulcan returned to Earth and attacked the X-Men, killing Banshee in the process. The X-Men battled Vulcan, who apparently knew some of them and had a mysterious connection with Cyclops. Answers were revealed, however, when the de-powered Xavier arrived. Able to walk again, Xavier revealed that Vulcan was Cyclops and Havok’s long lost brother, who Xavier had believed dead after a failed mission. The X-Men were shocked even more when they found that another member of Vulcan’s ill-fated team, Darwin, was still alive as well. Angry and a bit insane, Vulcan fled Earth and headed to attack the Shi’ar Empire, who he blamed for the death of his mother, among other things. [X-Men: Deadly Genesis #1-6]
Shortly afterwards, the energy field in space was suddenly pulled down to Earth and was channeled into a man in Alaska named Michael Pointer, who until that moment didn’t realize he was an energy channeling mutant. The deranged being that emerged called itself The Collective and went on rampage as the energy gained sentiency, killing members of Alpha Flight in the process. The Collective found the powerless Magneto on Genosha and then revealed that it was actually being controlled by the mind of de-powered Xorn, who revealed answers to questions concerning a recent attack on New York that Magneto was framed for. Xorn attempted to re-power Magneto before being defeated, though in the end Magneto was left missing and possibly dead. [New Avengers #16-20]
From the Ashes
With the world in need of guidance, there were those who rose to the occasion. In England, Captain Britain was alone with only vague memories of why he was no longer in Otherworld or what had happened to his missing wife, Meggan. Trying to make some sense of it, he was contacted by Pete Wisdom of MI-13 and agreed to reorganize the team Excalibur, as Great Britain needed heroes in the wake of M-Day more than ever. [New Excalibur #1-5]
In New York’s Mutant Town, X-Factor Investigations changed their mission statement in the wake of M-Day. While they would still do their regular detective work they would also work to find out the truth behind M-Day. The team ran across the de-powered Rictor who tried to commit suicide, but was convinced otherwise and joined their ranks. Soon they met the enigmatic Layla Miller, who for her own reasons did not want X-Factor to discover the truth about M-Day or to reverse it. [X-Factor (2nd series) #1-12]
Fully remembering the House of M reality, where she was a beloved hero known as Captain Marvel, Ms. Marvel decided to work her butt off to achieve it her full potential as a superheroine. She returned to the life of solo adventuring, even turning down an offer by Captain America to join the New Avengers as she wanted to do this on her own. However, the House of M’s inspiration was not the only thing Carol gained from that reality. 
In the changed world, Carol had a foe named Warren Traveler who was outside of reality in the instant that Wanda put everything back to normal. As such, Traveler returned to a post-House of M world deranged, as the magical energies he wielded were out of sync with the proper reality. [Ms. Marvel (2nd series) #1-5, New Avengers #15]
Wolverine also had a new outlook on life after the House of M. Thanks to Wanda’s actions Wolverine’s memory was fully restored, giving him access to his entire life. With these memories Wolverine began a quest to confront those from his past and also to unravel the secrets that still plagued him. During his journeys, Wolverine sought out old friends, and found that the de-powered Maverick and Jubilee ran a safe house where former mutants could meet. [Wolverine (3rd series) #36-40, Wolverine: Origins #6]
Belligerent Responses
The X-Men were unaware that weeks prior to M-Day, Reverend William Stryker came across a damaged Nimrod unit that traveled through the time stream. Accessing the memory files of the unit, Stryker used them to his advantage, targeting individuals that would help mutant-kind gain equality. Organizing his Purifiers, Stryker made ready an assault against the X-Men, particularly the students. [New X-Men (2nd series) #20-36]
Claiming to have been awakened by the de-powering, the ancient mutant Apocalypse rose once again. This time, his plan entailed unleashing his Horseman Pestilence on the world and killing off 90% of the world’s human population, and then having the last 10% of humans fight the remaining mutants for supremacy. [X-Men (2nd series) #182-187]
Other powerful mutant leaders were also on the move. Exodus enlisted a new group of Acolytes to serve him. Together they attacked the S.H.I.E.L.D. Helicarrier in order to use Cable to create a new Cerebro to see if any new mutants have been born since M-Day. Horrified, Exodus discovered that none had and his Acolytes escaped. [X-Men Annual (3rd series) #1]
Meanwhile, de-powered mutants were also making moves. Believing that the government was behind M-Day, a group of de-powered mutants came together to launch terror strikes in Mutant Town. This group named themselves the X-Cell. [X-Factor (3rd series) #17-20]
Rebirths and Returns
When Wanda warped reality, there was no way for her to know that her actions would spread further than just her own reality. The villain known as the Shadow King, who found himself trapped in an alternate timeline, found that the reality manipulations weakened the walls between realities. After defeating another world’s X-Men and enslaving them as his vile Dark X-Men, the Shadow King returned to his native reality and began to plan his schemes. [New Excalibur #8]
After the de-powering, the energy forces once controlled by Magneto and Charles Xavier mingled. Unknown to any of the heroes, the psychic essence of the dead villain Onslaught still existed in their world. Mingling with the powers of his fathers, Onslaught found himself reborn, and yearned for revenge against Franklin Richards. After being attacked by the vile creature, the boy used his powers to flee the planet to Counter-Earth, where Onslaught followed him and began to wreak havoc. [Onslaught Reborn #1-5]
During the House of M, the demon lord Belasco became aware of Illyana Rasputin’s resurrection. However, he lost track of her when she teleported to Limbo, shortly before the world was reverted back to normal. Bent on reclaiming the young girl who was once his pupil, Belasco apparently tried to re-create her, but he only succeeded in conjuring up her body and mind. Illyana’s soul still missing, Belasco led a revolt in Limbo before tracking down the last people he sensed were with Illyana before the House of M reverted: the students of the Xavier Institute. [New X-Men (2nd series) #37-41]
Another House of M survivor who departed from the main reality before the world returned to normal was the body-snatching Proteus. Blaming themselves for giving Proteus as means to escape, the Exiles chased Proteus to another reality, where he abandoned the decayed body of their teammate Mimic, whom he had possessed. Proteus began a long chase through realities where he would take over the bodies of innocent beings in order to find a host that wouldn’t decay. Finally, Proteus took over the Exile Morph, finding him to be exactly what he needed. Still, the Exiles were able to defeat Proteus by brain-washing him into thinking that he was Morph. [Exiles #72-82]