For decades, the Griffons have been at war with the ponies, not specifically the ponies though, just their ruler. They wish to free the ponies from their nigh brain-dead follower status of the fake-goddess tyrant that is Celestia. They have known that she doesn't do as she says she does, and have been trying to get the world to see it the way they've uncovered. By peaceful ways had seen impossible, thus they resorted to force. It has been a few years of terrible quietness on the front, but that is soon to end, with the only thing that could turn the tides, thrown into the fray.