The latest "Marvel History is Destroyed" teaser asks the question "Who saved Jean Grey from Dark Phoenix" with John Byrne's Uncanny X-Men #135 cover faded in the background.
In comic books, the long-held answer to that was the Phoenix Force itself. After Jean Grey died in the culmination of "The Dark Phoenix Saga. Years later, it was later revealed the deceased Jean Grey was a clone made by the Phoenix Force to inhabit before the on-set of the storyline. Jean Grey herself was put in a healing cocoon at the bottom of Jamaica Bay.
Marvel's teaser - like the others - alludes to major continuity changes in a new storyline (or storylines) that will 'destroy' Marvel history.
Look for more on this to be announced in the coming weeks.