House of M.
Superheroes aren't supposed to die. They're not supposed to lose their powers and get old like the rest of us. They're supposed to win and keep winning.
And they did win. They stayed young and strong. The bad guys lost, and we waited for the next issue. This narrative was working fine until M. Day. Somehow, the bad guys win, the superheroes lose, and we're left waiting for Wolverine to wake up and say it was all a dream. But there is no dream. This is the Marvel Universe's Earth-616.
I know it can be upsetting to see our favorite superheroes in actual danger, but we must accept that the events that occurred during the House of M. series affected almost every superhero within the Marvel Universe. While the time-line can be a bit confusing, understanding these events is an absolute necessity for readers who want to read Decimation, Legacy, or any other series that occurs after M. Day. Let me explain.
Essentially, the Scarlet Witch (Magneto's daughter) has a mental breakdown due to her inability to have children. During her breakdown, she kills several Avengers. Because of this, Professor X and Dr. Strange try to help her deal with her reality-changing powers. While Professor X and Dr. Strange are trying to help the Scarlet Witch, the remaining Avengers, a few of the X-Men and Spiderman set out to speak to her on Genosha. She panics and warps reality into an existence where everyone has been given whatever they want the most.
The superheroes eventually figure out what has happened and set out to confront the Scarlet Witch and Magneto. The Scarlet Witch freaks out again and says the words, "No more Mutants." This is known as M. Day.
I won't tell who loses their power, who dies or who lives. You'll have to read the book to learn that.
House of M. titles at the library: