Once upon a time, in the magical land of Equestria, there lived three princesses. The youngest princess brought about the beautiful, starry night to the land. The middle princess brought the bright, sunny day to the land. And the eldest princess brought the wind and plant-life to the land, also bringing the inhabitants the ocean.
Together, these princesses brought balance to the land. But it was not always like that.
The youngest sister grew jealous, and circumstances forced the middle sister to banish her to the moon. The eldest sister took pride in her younger sister for standing up and facing what she hated doing. But soon she became furious.
The eldest, who was destined for the throne, grew resentful. The ponies of Equestria had rejoiced in her sister's saving them, and had the middle sister take the throne instead. They completely forgot about the eldest sister, and she was but a shadow of her sister.
She travelled to the Everfree forest, sitting alone, going over her troubles. Nobody knows quite what happened while she was there, but she exited with many, many followers. She raged a war on her sister, confronting her in the midst of battle and demanding her rightful crown.
The two battled on and on, and when it was looking bleak for the younger princess, she retrieved the Elements of Harmony, and fought her older sister again, this time winning.
For her ignorance, she was banished to the Everfree forest with all of her followers, never to resurface.
However, some say she's lurking in the shadows, gaining power, getting ready for her return. And when she's ready, terrible war will rage over the land, until she has the royal crown upon her head.