Marvel Comics announced a new title for Legion will feature Marvel’s most powerful psychotic psychic. Details are being withheld until a special presentation at New York Comic Con, but the character has an established history within the Marvel Comics Multiverse.
Because he shattered it and created the Age of Apocalypse.
Given Marvel’s venture into the Legion TV series, it’s not surprising Marvel Comics would bring this character back for a series run (or mini series, more likely.)
In previous comics, before the iconic Legion’s Quest which led to the creation of the Age of Apocalypse, Legion suffered from a dissociative identity disorder. The character in the series has a different interpretation and, since Legion seemed to have resolved his DID before the start of Legion’s Quest, the Marvel writers would be equally justified in giving him DID or portraying him more like the series version.
Given the history, it seems likely the series will at least make reference to the Age of Apocalypse or Legion’s Quest.
Writers will also, once again, have to address a Legion “super death.” Legion accomplished what few characters have. Beyond dying, Legion recently erased himself entirely from existence during Avengers vs X-Men. But a fragment of his mind remained in existence, and Avengers vs X-Men is not even the first time Legion’s existence has been erased in such a way.
Gabrielle Haller, Legion’s mother, split it off with his father (Charles Xavier) after watching Legion die in a time traveling incident, implying Legion would never have been born in the first place.