The date is September the 19th 2552. The Halcyon class Cruiser "Filly of Autumn" exits a slip space jump after fleeing the Covenant's destruction of Reach; a Pony colonised planet on Equestria's doorstep that once thrived with Naval activity.

On the other side of slip space, the Filly of Autumn and the thousands of Ponies aboard her discover a mysterious alien ring world, as well as a new batch of Covenant warships.

As the Covenant board the Autumn with the intent of destroying it, Captain Rarity orders the soldiers and personnel to abandon ship, including the ship's AI, Twilight. Only one Pony on board is eligible to keep the AI Twilight safe, but she isn't exactly... "war material." Follow her as she is given the herculean task of protecting Twilight from the might of the Covenant juggernaut and the evil that lies in wait on the ring, with help from her friends and fellow Ponies who will give anything to protect her.

Follow Luna, Rarity, Celestia, Rainbow Dash and many more beloved characters as they are whisked into the shoes of the characters from Halo's The Mona Lisa. After salvaging a dying prisoner from Halo's debris played by Lightning Dust, the Ponies of the UPSC Red Horse are left curious and hungry for answers. Commander Princess Celestia and the AI Discord order Sergeant Luna and a squad of seventeen Ponies to investigate the ship Lightning Dust came from: An abandoned Prison Ship known as The Pony Lisa. So what happened on board The Pony Lisa? Did the Griffins playing the roll of Covenant take her over? Or was it just a prison riot? The answer is far more disturbing than anypony could have imagined. Whilst finding a few survivors on the way, and Luna fighting a separate battle in her head, the dwindling squad must push through a horrific infestation and destroy The Pony Lisa's nav systems to stop the evilest thing in the galaxy from locating colonised worlds.