A thousand years after the banishment of Princess Luna to the moon along with all the Imperialists who swore allegiance to her, a complex lunar society has been built beneath the surface of Nightmare Moon's prison. In just a few decades, the despotic Empress of the Lunar Empire will have gained enough power to return to Earth and invade Equestria, transforming it into a dystopian realm of darkness. The only thing that stands in Nightmare Moon's way is the fulfillment of a prophecy, where the stars will aid in her escape so that the Elements of Harmony may exorcise her of her evil before she becomes dangerous enough to overcome her sister, Princess Celestia.

Enter Myrk, the former Captain of the Lunar Night Wraiths. Once the chief bodyguard to Nightmare Moon, he has since been branded an exile and traitor to the Empire. The Imperial Lunar Rune Guard hunt Myrk throughout the subterranean cityscapes of the moon, until he is forced to hide within the sarosian district of Tranquility deep below the outer laters.

Now, after having reunited with his half-sarosian lover, Choral, Myrk must embark upon a dangerous mission to deliver a captured piece of Princess Luna's magical essence to the lunar surface, in order to cast a beacon that will summon the stars and pave the path towards Nightmare Moon's righteous defeat.

This is an indirect prequel that takes place within the same universe as The End of Ponies.