It is common knowledge that Twilight Sparkle was not the first of Celestia's apprentices, even if only recent times were considered. However, what is not common knowledge is that mi Amore Cadenza was not the only apprentice to precede the current Crown Princess of Cant'r Laht. Years ago, Sunset Shimmer was apprentice to Celestia as a backup in case Cadence didn't work out and kept secret from all but a few, but she too proved lacking to the ancient sorceress and mysteriously disappeared. When she returns to find another occupying the position she thought she was destined for, her actions will lead her replacement into another world, a world Sunset Shimmer is well familiar with, but Twilight Sparkle is not. Twilight will have to travel to the World Across the Divide, a world very different from the one she knows. Not only will she have to learn of Canterlot Academy, a militarized school in a nation on the brink of a Great War, but she will also need to learn how to control a new body, one without sorcery at that.

In the same universe as Camaraderie is Sorcery, to be read between the third and fourth seasons (after Chapter 3:14.3). The canon-universe equivalent is the Equestria Girls movie.