Talk:Princess Luna/@comment-26973802-20140602043755/@comment-24908786-20140603164519

Silly Filly Studios' "Fall of the Crystal Empire" does make it clear that Sombra might have had a part in influencing the manifestation of Nightmare Moon as he did foreshadow when Luna would become corrupted and banished by Celestia...

And we saw Celestia's worst fear, casted by Sombra, being Luna's fall to the Dark Side and becoming Nightmare Moon.