Prolouge

One thousand years ago Princess Luna was overwhelmed by envy and transformed into the monster known as Nightmare Moon. She then attempted to dethrone her sister Princess Celestia and cast the world into eternal night. The battle between the two was fierce, and in the end Princess Celestia was forced to banish her sister from Equestria, condemning her to a millennium of exile on the moon as punishment for the crimes committed she had committed. For many ponies that is all there is to the tale of the Nightmare wars, but there is one last remnant from those times. One other who was banished was quickly forgotten, becoming no more than a footnote in a long forgotten history book. After all, it was unimaginable that anything other than a princess could have survived a thousand years of banishment.

Deep beneath the surface of the world, in the farthest reaches of Tartarus, a disturbance is felt in the darkness. At first it is nothing more than a ripple, but as it begins to travel through the caves it quickly gathers in strength. Soon it leaves Tartarus behind, and spreads throughout the night of Equestria. The ripple-become-wave passes over the homes of ponies both great and small. It travels though lone huts and great cities. Finally the wave of power reaches the edges of Equestria, and as if it had hit a great wall it suddenly begins to travel back to its source. The wave rockets back over the sleeping ponies, it tears through streets and glides over homes, and as it passes it pulls the essence of the darkness with it, herding it back to the source of that original ripple.
Finally the wave of power roars back through the caves of Tartarus and converges on its source, and in an explosion of darkness something drops onto the stone floor with a thud.

The last remnant of the Nightmare wars has been freed.

Author's Note

Thanks to iisaw for editing and encouragement.