The House of M ended the same way it began. With a flash of white light the Scarlet Witch used her power to alter reality. The first time she was coerced by her brother Pietro (Quicksilver) and created a world where Mutants were dominant and ordinary humans lived in fear of persecution, giving rise to the House of M. The second time she uttered the words: "No more mutants", and with the flash of white the world she created reverted back to what it was before... almost. In that instant the mutant population was instantly reduced from millions to thousands, the majority suddenly realizing that they were powerless. These millions of former mutants are changed, reduced to normal humans in every way down to their DNA. The Scarlet Witch has completely erased the X-Gene from their genetic code. Those few that remembered the events of the House of M were those that were touched by the powers of Layla Miller during the House of M, revealing that the reality that the Scarlet Witch had created was not how things should be.
Because virtually none of the population was aware of what had actually occurred, the sudden de-powering of almost all mutants was met with varying reactions. The day with which the mutants were de-powered is alternatively referred to as M-Day or the Decimation. The term Decimation also became synonymous with the reduction of the mutant population due to the large reduction in their total numbers. In terms of the story-arch, the Decimation is the events that occur directly after the House of M that chronicle the fallout of the massive event. It spans several different comic book series, and is comprised of several different story-archs that are related in origin.
During the Decimation things became quite difficult for mutants, powered and de-powered alike. Now that their numbers were no where near as strong as they were before, human gangs began to violently attack many of the remaining mutants. Because of the hostilities, Cyclops offered the use of the Xavier Institute for Higher Learning as a sanctuary to any mutant in the world regardless of their history. Mutants friend, foe, and relatively unknown came to the mansion hoping for safety against the dangerous outside world. The mutants that camped out on the school grounds began referring to themselves as the 198. While this number did not accurately reflect the number of mutants left (or the number of mutants in the group), 198 was the earliest confirmed number of mutants still powered after M-Day.
Tensions grew at the mansion as the 198 began to feel more like prisoners than guests. The Office of National Emergency (ONE) had deployed their Sentinel Squad ONE at the mansion as a protective measure, keeping the mutants safe from outside threat. To do so they also were authorized in the use of force to keep the 198 from leaving the school grounds. Only the secretive Mr. M seemed to have the power to stop the Sentinels, which he demonstrated at one point by hurling two sentinels out of the way to prevent one of them from stepping on a butterfly. Seeing what awesome power Mr. M possessed, ONE determined that he was a threat and needed to be dealt with. After much tension and pushing from both sides the 198, under the leadership of Mr. M, left the school grounds with the intention of creating their own island settlement under their own protection and governance. The sentinels were powerless to stop him, but ONE had a foothold within the group. The mutant Johnny Dee had used his power over the duration of his stay with the 198 to create voodoo doll replicas of many prominent members of the group. With these dolls he could control the actions of those individuals. Taking control of leech and magma he was able to neutralize Mr. M's powers, and destroy him in a rush of molten lava.
For more information see the 198.
Son of M
Quicksilver (Quicksilver) is de-powered after the House of M. It seems to be a fitting punishment after convincing his sister to create the House of M. Formerly living life permanently in the fast lane, Pietro is now forced to live his life at the painfully slow pace of a normal human. Pietro travels to the Moon to visit his Inhumans wife and daughter, Crystal and Luna. While in the Inhuman city on the Moon, Pietro is given the idea to re-power himself with the Inhuman Terrigen Mists. After exposing himself to the mists, Pietro believes that nothing has happened. He is confronted by a disheveled, future version of himself who tells him that the mists have not only given him back speed, but have given him the ability to jump through time by vibrating his body at high rates of speed. He hatches a plan to steal the crystals that generate the mists and take them back to Earth.
On Earth Pietro exposes himself and his daughter. Luna was disallowed the rite of Terrigenesis by the Inhumans because her being half human made exposure a risk to her health. Believing it to be his fate and duty, Pietro then took the crystals to the island of Genosha to begin his quest to re-power the world's de-powered mutants. He exposed several former mutants on Genosha to the mists with devastating results. His father condemns his actions, and for his disregard for the safety of those he exposes to the mists. The U.S. government intercepts him and takes control of the crystals. Black Bolt, the leader of the Inhumans asks for the crystals back and is told by SHIELD that they are now the property of the U.S. government. The Inhumans take this threat to their culture and tradition as an act of war and declare war on the government of the United States. These events lead into the Silent War storyline.
For more information see the Son of M.
It was noted by both Beast and Hank Pym that the energies of the de-powered mutants needed to go somewhere rather than simply ceasing to exist. When the Scarlet Witch de-powered the majority of the earth's mutants, the immense power was collected into the body of Alaskan mutant postal worker The Collective. Michael had no idea that he was a mutant. His power was to absorb the energies of others, and his body instinctively reacted to the ambient energies of the de-powered mutants in the Earth's atmosphere and absorbed them. This immense load of power channeled into Pointer's body destroyed the post office and everyone in the vicinity. Amongst the energies which had been ambient in the atmosphere was the consciousness of the deceased mutant Xorn. When he absorbed these powers, Xorn was able to take possession of Pointer's body. Most likely realizing what he now was, Xorn seeks out Magneto who was de-powered on M-Day.
Xorn in Pointer's body (now the being known as the Collective) begins to travel down from Alaska through the Canadian wilderness on foot. The Collective is confronted by the Canadian Super-Team Alpha Flight in an attempt to stop him. In almost no time the Collective laid waste to the entire team, leaving them dead in the snow (with the exception of Sasquatch who was presumed dead but survived because of his healing factor). Unfazed, the Collective continued South. It was Spider-Man, being one of the few involved in the House of M that retained memory of the event, who initially figured out the Collective's origin when he realized that the powers he was exhibiting seemed to be those of the mutants de-powered on M-Day. At the time Spider-Man is on a SHIELD Helicarrier. He is rescued by fellow members of the New Avengers, but not before S.H.I.E.L.D. telepaths were able to probe his mind to discover the truth behind the House of M.
In America the Collective moves through New York, continuing to ignore the pedestrians encountered on his trip. When he was attacked by the New Avengers he realized that he was able to fly. He is taken into space by the combined efforts of Iron Man and the Sentry but, again, has little problem circumventing the two when he hurls the Sentry into space and flies back to Earth. He heads straight to the island Genosha where he finds Magneto. It was there that the Collective revealed that it is being controlled by Xorn, whose personality was able to dominate Pointer's own. Xorn explains that he sought out Magneto because the mutants are in need of a leader, and that they will follow Magneto's lead. Xorn re-powers Magneto. Magneto, no longer in control of his body begins to battle the New Avengers. Not wanting to be someone else's pawn Magneto begs the Avengers to kill him. He is taken down by S.H.I.E.L.D. agent Daisy Johnson who uses her power to create a tremor in Magneto's brain, separating the collective entity from him. The Collective is hurled into the sun by the Sentry, separating Michael Pointer from Xorn. Pointer and Magneto are both separately taken into S.H.I.E.L.D. custody and the helicopter carrying Magneto's body explodes in mid air above Genosha.
A startling revelation is made by a figure from the X-Men's hidden past. When the original team of X-Men consisting of Cyclops, Beast, Jean Grey, Iceman, and Angel are captured by the island mutant Krakoa it was originally believed that Professor X assembled the new team of X-Men from around the world for a rescue mission. While these events did occur in this manner there was a first rescue team dispatched to Krakoa prior to the all-new all-different X-Men consisting of several of Moira MacTaggert's students: Petra, Sway, Darwin, and Vulcan (youngest brother of Havok and Cyclops). This team was young and inexperienced and met with a quick defeat by the island. It was after this first rescue mission that Xavier gathered together a group of older, more experienced mutants from around the world. After the second team rescued the original X-Men, Krakoa was lifted into orbit by Polaris. The deaths of the first rescue team weighed heavy on the hearts of the X-Men so Xavier decided to remove the memory of the original team from the surviving X-Men. Only Vulcan survived having absorbed the powers of his fallen comrades, and remained in stasis on the island.
After the Scarlet Witch de-powered most of the world's mutant population when ending the House of M, the energies of the de-powered mutants released back into the universe caused Vulcan to awake. Knowing what had happened Vulcan began to attack the X-Men, first psychologically and then physically to draw Xavier out (who had not been seen since before the House of M). Vulcan forced the de-powered Xavier to show his students what actually occurred surrounding the Krakoa incident. Before the X-Men were able to attack, Vulcan flew into space to make the Shi'ar pay for the traumatic childhood they caused him. The events of the Deadly Genesis lead directly into the Rise and Fall of the Shi'ar Empire.
For more information see the Deadly Genesis.
After M-Day a large portion of the students at the Xavier Institute for Higher Learning are left powerless. Emma Frost disbands the teams of students and collects those whose powers remain in the danger room for an impromptu session to determine who will remain on a single squad of young X-Men trainees (the New X-Men). After a quick but intense battle session, the new team is selected. It is also decided that because of increased hostilities against mutants since M-Day, it would be safer for the de-powered students to be sent home rather than remaining at the institute. With the exception of Prodigy, 42 de-powered mutants are loaded onto a bus to be taken away which, once full, explodes. This attack was perpetrated by long-time enemy of the X-Men, and political and religious crusader against mutants:William Stryker. Stryker was aided by the remains of the future Sentinel Nimrod, whose memory banks are used to determine which of the surviving mutants to target. After unsuccessfully attempting to murder Dust, Stryker and his "Purifiers" are stopped by the New X-Men during an assault on the mansion. In order to stop Stryker, Elixir reversed his powers from a healing touch to a death touch, killing Stryker. The New X-Men then discovered that the remains of Nimrod had gone after Forge to force Forge to build it a new body.
While the New X-Men were on their way to rescue Forge, Forge was able to trick Nimrod into downloading its personality into a prototype body which Forge had built. This new body had built-in safe-guards which prevented Nimrod's programming from taking over its new body. Misunderstanding what had happened, the New Mutants attacked the robot which released Nimrod's primary programming allowing it to attack. In the battle against Nimrod both Rockslide and X-23. Rockslide's body was obliterated Nimrod's blasts, but was re-assembled by his teammate Hellion's telekinesis. X-23 was badly burned while destroying Nimrod's body, and her healing factor was unable to cope with the damage. Hellion flew back to the mansion, only able to make it back in time when Emma Frost used her telepathy to remove mental blocks allowing him full access to his powers. Back at the mansion Elixir was able to use his power to assist X-23's own healing factor, saving her life.
Related Story Arcs
House of M - Precedes and creates the events of the Decimation.
Rise and Fall of the Shi'ar Empire - Events following the Deadly Genesis storyline.
Silent War - Events following the Son of M storyline.
Endangered Species - upcoming With the numbers of mutants in the world reduced from millions to thousands on M-Day, mutants are on the brink of extinction. With no new mutants occurring in the human population will this be the end of mutant kind, or a new beginning?