Talk:Princess Luna/@comment-11498358-20131124141106/@comment-26973802-20131124193306

I'm not so sure about Nightmare Moon originating as a separate entity (and she's established as such to the ponies in the comics from her lines yet in the S4 premier, as far as Twilight knows she's only Luna corrupted, Twilight never calls her Nightmare Moon)

What I think, the outside force (Sombra maybe?) magnified her jealousy slowly leading to increasing bitterness and when it reached its highest point, all Luna needed to do was take the final step (trying to overthrow Celestia and bring eternal night) for it to manifest into a form of its own and possess her.