Decimation (comics)
Decimation is the late 2005 Marvel Comics storyline spinning off from the House of M limited series. It focuses on the ramifications of the Scarlet Witch stripping nearly all of the mutant population of their powers, thereby reducing a society of millions to one of scant hundreds.
This event, which occurred on November 2 according to X-Men (vol. 2) #191, is known as "M-Day" in the Marvel Universe.
Read more about Decimation (comics): Overview, Criticism, Depowered Mutants, Confirmed Remaining Mutants, Deceased Mutants After M-Day, Mutants or Not, Consequences, Repercussions