The so-called parallel universe means that there are countless multiverses besides the Marvel universe of the main line, so that you can draw some plots that do not affect the main line universe. For example, Deadpool, who broke the dimensional barrier, realized that he was just an anime character after being experimented by the bad guys, so he killed all the heroes in his universe, such as Hulk, Iron Man and Captain America. After killing all the heroes in the world, he once again.