Cover art for the story Spectral Eclipse by ReluxtheRelux
a story about a alternate universe where Dusk Shine(R63 Twilight sparkle) is serving Nightmare Moon as her inquisitor.

Story synopsis: Almost six years have passed since Celestia's defeat at the hooves of Nightmare Moon. In these six years, Queen Nightmare Moon established Equestria's dominance over its neighbors under her iron hoof.
Just one week before the 6th Nox Eterna Festival, there are still underground insurgent groups opposing her. Among them, there is a terrorist known as "Ghost" who has grown increasingly active in the month leading to the festival.

Dusk Shine, pupil of Her Majesty Nightmare Moon, is assigned to aid the Lunar Inquisition in finding the "Ghost" where they last struck: Ponyville.