Years have passed since Princess Celestia's prize student, Dusk Shine ascended to the role of Equestria's first Alicorn Prince.

Hardships had plagued the young stallion's first couple years on the throne, but Dusk has continuously proven his mettle during each crisis earning him the respect of his peers and the common pony alike. Yet, he harbors a secret that could shatter not only their image of the alicorn, but possible their faith in the newest royal.

A dark secret that hides in the old castle ruins of the Everfree Forest...

First story with depictions of sex in it.
Rule 34, Rule 63 Twilight

Based off My love, the Night By Discored Flare

Celestia lore based off this classic: Princess of the Stalls

Cover art is by radomartxx01 on Derpibooru.

An entry to Dezmos NSFW contest.

EDIT: Contest results for Dezmos NSFW contest are in and can be found here.

I received Judge Kalash93's overall personal pick:

I am very impressed with this story. It’s not quite like anything I’ve ever read before. The term I would use is literary. The focus is not on the sex, but rather on the characters. So what? So it’s not a common pairing to have R63 Twilight Sparkle with Nightmare Moon. If Nightmare Moon isn’t some kind of hentai futa tentacle rapist on sight with everyone, then she’s Celestia’s merciless domme, or she gets the defrosting treatment to come across as much more normal and friendly than her canon depiction.

Here, however, she keeps her canon aggressiveness and attitude, despite being in what definitely counts as a romantic relationship with Dusk Shine, where they are to some extent hostile and also coexisting. The prose is also of a higher order, using more sophisticated words and devices than is common in fanfic. This creates a mildly eerie tone as the reader is never quite sure as to the state of the relationship and whether or not Nightmare Moon is actually a threat, she keeps her taste for violence and a threatening voice, but not always supported by her actions.

That is interesting is how Dusk Shine has learned how to read her, and rather than forcefully reform Nightmare Moon, Dusk Shine has instead chosen to learn how to live with her. I don’t know if what either of them feel for each other could be called love in the conventional sense, but there is a sense of a bond and of definite trust. It’s not romantic nor lustful like most other sex fics, it’s a unique feeling. Further praise goes to this being a gaiden story to a much longer story which neither gives nor requires a weighty tome of exposition be hurled at the reader before engaging, yet is understood well enough by the implicit premise of it being fanfiction so just roll with it. All in all, this is an intriguing story that both embraces and elevates the art of fanfiction.