The annexation of Crystal Empire by Changeling Kingdom was the most severe blow that Equestria had suffered since Princess Celestia was force to banish her sister to the Moon. While that had been most internal affair, this had more profound effects that altered the delicate balance of power for the benefit of Changeling Kingdom, and severely strained Equestria's diplomatic relationships with all of her major neighbours.



This also irrevocably revealed that Queen Chrysalis never had given up her dream of taking over all the lands of the ponies. After the defeat of direct invasion four years before the annexation, she seem to have recovered her forces, and now the weakened Equestria could do a little than wait her next move...

- History of Equestria, vol. VIII