The Princesses have a recieved a letter from the Diamond Dogs. A letter of peace, saying that they have agreed to stop their attacks on the ponies of Equestria. They've agreed to send an ambassador for their race, and the Princesses were more than happy to oblige. Even though Celestia's gut knows something's off, she's decided to keep it to herself, not wanting to ruin this great opportunity.
I did not create the cover image! All credit goes to Lucky978 on DeviantArt for creating it.