When the eternal di-archs of Equestria are suddenly and brutally assassinated, the country becomes wracked with grief and unstable, and the celestial bodies stop moving. In an attempt to provide stability, leadership, and a solution to the problems that keep cropping up, Twilight and Cadenza take up the now empty role of the Equestrian Diarchs.

This may read more history like than anything, and will not be very focused on the day to day of the characters