"Identity. A word. A concept. It is what separates us from everypony around us. It makes us unique. It encapsulates our strengths and our weaknesses. It makes us individuals. Each of us separate beings.
Yet we are all just a small part of something bigger. We are blood flowing through the vessels of this world. By ourselves we are a speck on the plane of time, but together we make the world. We are the world."
-Starswirl the Bearded. From 'The Understanding of Time, Vol. I'
Prologue
Once upon a time, in the magical land of Equestria, there were two regal sisters who ruled together, and created harmony for all the land. To do this, the eldest used her unicorn powers to raise the sun at dawn; the younger brought out the moon to begin the night. Thus, the two sisters maintained balance for their kingdom and their subjects, all the different types of ponies.
But as time went on, the younger sister became resentful. The ponies relished and played in the day her elder sister brought forth, but shunned and slept through her beautiful night. One fateful day, the younger unicorn refused to lower the moon to make way for the dawn. The elder sister tried to reason with her, but the bitterness in the young one's heart had transformed her into a wicked mare of darkness: Nightmare Moon. She vowed that she would shroud the land in eternal night.
Nightmare Moon, now fully consumed by rage, fought against her sister in the black of night. She enlisted the aid of the Nightguards, the fearsome bat ponies in the fight against her sister, to whom the pegasi, the unicorns and the earth ponies were all allied.
And so for a fortnight the first war in Equestrian history raged, and all around them the land died, deprived of their precious sunlight. Nightmare Moon, aware that she was vastly outnumbered, sought to strike a killing blow on her sister: she would take Canterlot. But the elder sister had other ideas, and before the order could be made, Nightmare Moon found herself in the Everfree Castle, transported by powerful magic. There, the sisters fought, evenly matched, deadlocked, until dawn came.
Aware that something was wrong, Nightmare Moon attempted to flee, but before she could make her escape, her sister unleashed a power they had vowed never to use: The Elements of Harmony. The unbridled power of the elements was too much for just one pony, and instead of killing the younger sister as intended, she was banished to the moon.
From then on, the elder sister took on responsibility for both sun and moon, and harmony has been maintained in Equestria for generations since.
But now... it would seem history is destined to repeat itself. The darkness is gathering on the horizon once again, and Equestria is about to face the most formidable enemy they have ever seen.
Black and White