Nightmare moon theory · 6:21am Mar 26th, 2017
Many people have much theory about the dark entity known as Nightmare Moon some state she is a sister that got turned into a demon Others a mythical god without an actual form this theory though is mine.....
Theory: because of the chaos discord caused made it dangerous to go out at night so people would hide away from the dark because of fear of what's inside hoping for the next day which brings hope to their hearts after. Thus makes them lean more to the one who brings up the sun while fearing the one who brings the night, Over time a 'demon' finally noticed the spike of sadness and anger from Luna were it proceeded to haunt her. Slowly making its way into her subconscious where it starts, to convince to give control by saying they do not respect her enough or we should make the night longer to show them it is not as dangerous as they think. When Luna still refuses the demon starts growing the negative feelings inside making here hate more until she is almost depressed finally Luna gives in on a deal that the ponies have to appreciate the night, so the first thing nightmare moon does try to finish her end of the deal so she can complete her goals. She tries by making the night last forever, so they will have to, but there's a problem Luna's sister is just as strong as her, so she decides she needs to get rid of this nuisance, but she underestimates Celestia's will to protect the ponies and gets banished to the moon. The demon then starts to hate Celestia more and more, but since the demon never struck her end of the deal, she came back half as powerful as the Diablo use to be. When Twilight and here friends used the elements of harmony on her without all the power, she cannot keep holding on any longer and is banished to the 'nine circles of hell' from their world. Effectively being put down for awhile but you can't just get rid of something she will return sooner or later maybe in a different pony, but she will be back.
This is my theory hope it makes senses.