The Rise and Fall of a Universe: The Author
Almost all of the known Multiverse is constructed from what I label as Literary Universes, or a Universe that directly reflects a world depicted in a book, movie, or webcomic. It is commonly believed in Multiverse Study circles that, instead of mirroring the stories, these Literary Universes are the actual worlds direct from the books, movies, etc. Of course, since these Universes exist because of their stories (the most likely theory), it stands to reason that the authors of the stories are thus in total control over what happens in their universe, at least at the points in history that their books cover.
One of the main reasons why inter-universal custom dictates that, just as one should avoid affecting too much should they find themselves in their own pasts, one should also avoid interfering with major citizens/characters of another Universe because such actions may annoy or even existentially insult that Universe’s Author. Of course, with the original Author’s permission and occasional guidance to try and maintain stability, multiple Authors can affect a single Universe. A prime example is the Star Wars Universe, which has a plethora of Authors each telling a different part of the Post-Episode VI history of that galaxy far, far away (like far across the Void).
Some Multiversal Laws such as the definition of a Parallel Universe can be slightly altered at an author’s discretion. Only by an author’s influence can one part of the dimensional pair survive its partner’s destruction. In fact, most aspects of the general Multiverse Laws are bent and twisted by authors, mainly because they are blissfully ignorant of the Laws. Still, no one can fault an Author for the construction and ultimate destiny of his personal Literary Universe, not even those silly Critics.