(Can be read without first reading the prequel.)
Centuries ago, in the years after Nightmare Moon's banishment, Luna and Celestia's descendants helped Celestia build the new nation.
Luna's great-granddaughter, Gale Glider, forged the Royal Equestrian Coast Guard, imbuing it with traditions of valor, sacrifice, and bravery. Her final words remain their sacred oath:
"We have to go out. We don't have to come back."
Preread by Sledge115 and RDT, thank you!
Cover art found on Google without any attribution, alas.