Anyone who has sought counsel from Princess Celestia has met Raven, her most faithful aide. She has been a veritable second shadow to the princess for as long as the castle staff can remember... longer than they can remember, in fact. Much longer.
Princess Celestia sends her student, Twilight Sparkle, to the Royal Library to retrieve a mysterious book. What Twilight finds is an adventure she never could have expected.
As punishment for her crimes, the Elements have cursed Sunset Shimmer to do favors for anyone who asks. Lucky her. And then there's that other Twilight Sparkle she keeps running into...