Nightmare Moon



Nightmare Moon is another form of Princess Luna. When Princess Luna was overcome with jealousy, she turned into Nightmare Moon, whose personal goal was to bring about nighttime eternal. Princess Celestia imprisoned her in the moon for a thousand years, making it impossible for her to unleash eternal night. But she escaped a thousand years later, thus trying yet again to bring night forever. But the six ponies wielding the Elements of Harmony tried to defeat her, and won over her, turning her back to her real self. Princess Celestia then invites her to rule with her again, and she agrees, apologizing to the princess.

Depiction in the series
Nightmare Moon the very first antagonist introduced in the show, and is a momentary character, unlike most other characters. She is only Nightmare Moon for a extremely short number of episodes (this number being roughly two episodes, and three if you count Luna Eclipsed where she appears, again momentary because Luna turns into her in order to make the children like her.