@Align  
Not exactly. Luna gives that initial explanation in comic #5 to the others, but Luna admits to herself she was lying about it in comic #5 and #6, and in #8 she comes clean and admits to everyone she lied, and that Nightmare Moon and the Nightmare forces ALL come from her psyche and magic.
 
For any dragonball or dbz fans, after the Elements of Harmony were used on her, Nightmare Moon essentially became King Piccolo and possessed Rarity after she regained enough power. All the Nightmare forces including Nightmare Moon were born from Luna’s own negative emotions and power manifested. Tropes of this character can be found anywhere.

@Niggoslav_Krawczyk
 
SO IT BEGINS.

@Villain Pony  

@Background Pony #B40D  
Wasn’t that retconned to be quasi-demonic cloud possession?

@Villain Pony  
Ragyo Kiryuin. Kill La Kill, check it.

@Niggoslav_Krawczyk  
Discomilf?

@PonyPon Celestia confirmed for bigger and better threat to poniverse than Discomilf

@Background Pony #B40D  
At least she only almost killed one dimension.

Aw, Sisterly Love!

@Albus Fahrenheits I hope that implies someone is VATSing this shitty arc finally.

Something more people should keep in mind. Luna flipped out and became Nightmare Moon from her own feelings of jealousy and loneliness, after all, the princesses are not infallible.
 
If anybody’s going to try to have their cake and eat it too, it’s Celestia.

@The Smiling Pony  
It’s the Mysterious Stranger.

background pone: i’ll call it…Princest

@Yoga is boring  
It’s an Observer.

Is that slenderman?