A long time ago, two sisters ruled over the land: one held dominion over the day, and the other commanded the night. They quarreled, and to solve their dispute, they did something petty. They split the planet in half. They stopped the rotation of the planet—tidally locked it—so that one side would always be night, and the other always day.

Rarity is a member of the Corona Empire's parliament, sworn to do what is best for her country. One day, Queen Celestia summons her for a private talk. She asks Rarity to do something unthinkable, unfathomable, unheard of: deliver a message to the leader of the Nightscape, Queen Luna.