Is everything truly as they seem when a country's proud ruler has much to answer for?

One thousand years after the battle between the Royal Pony Sisters and the Lord of Chaos, Discord. Equestria has come to know a time where peace and prosperity reign supreme. Where despair and misery were few and far between. Friendship and camaraderie are commonplace among the population.

And, almost as an omen for a chain of faithful events to come, a forgotten civilization returns before the face of the world, fueled with vengeance and resentment towards their former equine brothers and sisters. More importantly, their former matriarch, Princess Celestia. Thrust from the city at its behest is a young soldier named Melpomene, blessed with unmatched skills in the battlefield, charged with the duty of learning of the outside world. And in turn, learn of her own city.

Things come into full circle when the mysterious Melpomene's life intertwines with that of Twilight Sparkle and their days spent together rouses the devout unicorn's interest, leading to a series of queries for Celestia that take her aback. Compelling her to confront a matter that once was thought to have been escaped from. A situation that has festered through the passage of time.

What has the princess of Equestria been hiding for so long? What will this mean for Equestria? For this city? What will the future pose for Twilight and Melpomene?