The Emissaries are handpicked to represent the human nation of Acadia, to the unexplored west, in Equestrian society. The Sun Emissary is tasked as Princess Celestia's secretary, logging archives, coordinating peace, and otherwise being in places she can't be at the moment.

The Moon Emissary, on the other hand, is more of what the Acadians would call "an enforcer," but the Emissary knows that without him, humanity would run rampant across the land. And they do, running from Acadia's laws to where they believe the laws are lax, and they can do what they want with impunity. To his kin, he is a traitor. To Equestria, he is the judge, the jury, and if need be, the executioner.

The most recent Moon Emissary is Aydin Ambrose, and after an investigation into several kidnappings, he becomes embroiled in a conspiracy that will test his loyalties; save his people, or save the ones he has sworn to protect?