There is a Marvel graphic novel called "The Sentry".
It was originally marketed as a old character that Stan Lee had "forgotten" that he created... that the character is from the early days of the Fantastic Four.
In the story itself, the main character is an aging, depressed man with a bit of a drinking problem. At night he has dreams as if he was a superhero... and then strange things begin to happen to him while he's awake.
*** SPOILERS ***
He begins to remember that he was a superhero named Sentry... and that all the rest of the superheroes (and the rest of the world) had forgotten him. He starts to investigate what happened and why the world has forgotten him... and this dark force starts moving across the globe. The Void has returned. Sentry's arch nemesis.
As Sentry re-introduces himself to all the heroes and tries to figure out who blanked him out of everyone's consciousness, Reed Richards of the Fantastic Four begins to remember what happened and why Sentry had been removed from everyone's memory.
The Sentry was such a powerful superhero that his powers split into two forms... his heroic side and the Void. The "two" of them were constantly battling because it was all playing out in Sentry's subconscious. Like a game that plays out in reality and the world experiences all the damage from his game. Once Sentry realized how dangerous the two sides of his personality were, he devised a machine that would transmit a signal, clouding everyone's memory that Sentry or the Void ever existed. So it wasn't a conspiracy... Sentry blanked himself out of existence for everyone's safety... and he would have to do it again to stop the battle between the two halves of himself.
Later it was revealed that this was the concept from the beginning, and Stan Lee agreed to promote this like a "found" story.
