Erin read on. After the Nightmare Moon incident (where, apparently, Celestia had used something called "the Elements of Harmony" to banish her sister to the moon, whatever that meant), Equestria had been fairly peaceful. A few hundred years after Luna's rebellion, there was a near-war with the expanding Griffon kingdom, which another princess, apparently also called Celestia, managed to avert. That was by far the most interesting thing that had happened in the intervening years, at least according to this book.  