After the events surrounding the Friendship Games, Sunset and Twilight discover that they have full control of the sun and moon of the EG-verse. SPOILER WARNING (anthro because of transformation here and there)
Twilight accidentally over-shot a spell, which went straight through the portal and by pure chance hit Sunset. Well, so much for band practice. Hooves aren't exactly made to play guitar.
When space-time breaks in a way it usually doesn't, Discord and Applejack end up racing through dimensions, trying to find a way back home. If home still exists...
Principal Celestia and Princess Twilight aren't stupid, they know the human government is going to be interested in the portal, so the Princess sends an envoy to be her voice to the human world...so why'd she pick Trixie?!
For years, Twilight felt that something was off within her. With the emptiness more pronounced than ever, she decides to confide in Celestia. What the princess reveals, however, will test their relationship to its limits.