No one knows where they came from. All they know is that they desired one thing: the taste of humans.
The beasts known as equines soon conquered most of the known world.
But humanity is known for its tenacity. Though clearly outmatched in both might and numbers people were able to hold out long enough to figure out ways to repel the hordes of monsters.
Equestria found its answer through power crystals placed in strategic places near the border. Powered up they provide a barrier that is capable of disintegrating any equine that gets too close.
The barrier has stood for generations and protected the lands of Equestria, but when and incident in the Everfree lets a band of monstrous equines into the heart of the country, a conspiracy long brewing begins to unfold.