In a separate universe, Sunset Shimmer and Twilight Sparkle were born into the world as alicorn princesses, twin daughters of Empress Celestia. One day, they were sent away to Ponyville, where they were destined to meet 5 special ponies.
Celestia has had it rough, raising both the Sun and Moon all by herself. She has had no choice given her sister Luna's recent banishment. Not to mention the emotional stress. Perhaps she has taxed herself a bit too much...
As her sister's wedding draws near, Luna begins to question about the curse of immorality. Thankfully Celestia is there to tell her and her groom to be about someone long since gone.