The Fallen Princess of the Night (Hazbin Hotel/Helluva Boss Harem x OC)

Princess Luna and her elder sister Princess Celestia were members of Heaven's guardians. When it's time for the inhabitants in Heaven to go to sleep, she has the ability to raise the moon. Everything was perfect, but that didn't last long since Luna uncovered a sinister secret that only Sera, the Exorcists, and Adam knew about, leaving everyone else in Heaven in the dark. The Extermination. Luna addressed them, horrified, telling them that it is wicked and wrong to slaughter sinners in Hell. Her sister was also alarmed when Luna informed her about it. Luna was then sentenced to Hell as a result of her questioning them, leaving Princess Celestia devastated to watch her dear sister go.

After being banished to Hell, Luna vowed to defend those who had sinned, built her own empire, and attracted the interest of several demons and sins. Will she ever get to see her sister again? Who knows.