She continued reading, getting more and more confused as she went. Apparently, the royal sisters had shown up to battle some malevolent force or deity known as Discord, which was making ponies' lives miserable back then. They had shown up and imposed order, then took over the nation. It sounded like an allegorical tale to Erin. Probably Discord was some sort of internal strife between the pony tribes. And then the sisters showed up, most likely at the head of an army, and took things over, imposing order like the Romans did in Europe a couple thousand years ago. 