Decimation, sometimes called M-Day, is the event, a direct result of the insane Scarlet Witch, when roughly 90% of mutants on Earth lost their powers.


"Decimation" began with the self-titled one-shot Decimation: House of M: The Day After, and heralded the relaunch of the Excalibur team in New Excalibur, focusing on Pete Wisdom looking for Captain Britain to head up a new British super team, as well as the relaunch of X-Factor from the MadroX miniseries. It also includes several mini-series - Son of M starring a depowered Quicksilver, Generation M focusing on other depowered characters, Sentinel Squad O*N*E showing the latest iteration of the mutant-hunting Sentinels to be robots piloted by humans, X-Men: Deadly Genesis, and X-Men: The 198 - and continues throughout the Marvel Universe, particularly in the X-Men-related titles. One consequence is an upswing of anti-mutant sentiment, especially among certain religious groups, who consider M-Day to be God's judgment against mutant kind.

It has been confirmed by various sources that there are considerably more than 198 mutants remaining - the number has been referred to as "symbolic" rather than actual, and in The 198 Files is said to be the earliest confirmed number. Numbers for pre-Decimation mutants vary from "over a million" (House of M #8) to 14 million (New X-Men #115, where it is said that the 16 million mutants who died on Genosha was around "over half" of the estimated global mutant population of 30 million mutants), giving a population, if the commonly-used 90% depowered figure is true, of between one hundred thousand and one and a half million. Based on the mathematical comparisons of the oft-repeated 198 and several million, Marvel has recently reevaluated the 90% figure into "Over 99%". This is shown in Civil War: Battle Damage Report when Iron Man comments on the Post-CW world.[1] The figure may be reevaluated again depending on events taking place in the upcoming Endangered Species and Messiah Complex storylines.

Both Hank Pym and Beast note shortly after the event that it is impossible for the energy that certain mutants controlled to simply have vanished, and that it must have been "sent" somewhere. As would later be revealed in New Avengers, most of this energy became a sentient entity called "The Collective", who has since come into violent conflict with the Avengers. In addition, a portion of the energy revived the body of Gabriel Summers, who had been trapped in space for many years following the defeat of Krakoa.