The 'mlp nightmare moon wins' fanfic could explore different character arcs. For example, Twilight Sparkle might have to face a greater challenge in her quest for knowledge and friendship. Other ponies would also be forced to adapt to a world where Nightmare Moon's will prevails, and their values might be put to the test.
I haven't read this specific fanfic in detail. But generally, in fanfics about Nightmare Moon's return in My Little Pony, they often explore themes like redemption, the struggle between good and evil, and the impact on Equestria. It might show how the ponies deal with this new threat and perhaps how Nightmare Moon's character develops during her return.
In MLP Nightmare Moon fanfics, the theme of forgiveness can be quite prominent. The other ponies in Equestria may have to decide whether to forgive Nightmare Moon for her past actions. And there's also the theme of self - discovery, as she discovers new aspects of herself during the course of the story.
Well, there's a fanfic that I really liked called 'Nightmare Moon's New Path'. In this story, she teams up with Twilight Sparkle to face a new threat to Equestria. It's interesting to see how their relationship develops throughout the story. There are also some fanfics that explore her relationship with the other princesses in a more in - depth way.
A plot might revolve around the friendship of the main ponies being tested. With Nightmare Moon in power, they could be separated or forced to betray each other. There could also be a plot where Nightmare Moon discovers a new threat that she needs the ponies' help to face, despite her victory, leading to a strange alliance.
The fanfic could be unique in how it weaves the plot. Maybe it combines different story arcs from the My Little Pony universe in a new way. For instance, incorporating elements from different seasons or specials to create a fresh narrative around Nightmare Moon's return. Also, the use of unique writing styles, like a more poetic or dark tone, can set it apart from other fanfics.
The themes of forgiveness and acceptance are quite common. Twilight may have to forgive Nightmare Moon for her past actions and accept her as she is or as she can be. Inversely, Nightmare Moon has to accept Twilight's offer of friendship. There's also the theme of self - discovery. Nightmare Moon might be on a path of self - discovery with Twilight guiding her, learning about her true nature and place in Equestria. And sometimes, there's a theme of facing a common enemy where they have to put aside their differences and work together using their unique magical abilities.
One idea could be that the OC is a new pony in Equestria who has the ability to sense the lingering darkness of Nightmare Moon within Princess Luna. The OC could befriend Luna and help her fully come to terms with that part of her past, leading to a stronger and more confident Luna.
The OC can be integrated as a helper. For example, if the story is set during the time when Luna is still struggling with the Nightmare Moon part of herself, the OC could be a kind of spirit guide, showing Luna the way to fully embrace her two sides and find balance.
Well, 'Twilight and Nightmare Moon: A New Beginning' is a fanfic that's quite interesting. It starts with Twilight accidentally stumbling upon an ancient spell that has a connection to Nightmare Moon. As she tries to figure out what to do with it, she gets drawn into a journey where she has to interact with Nightmare Moon. This leads to a series of events where they both learn from each other. And then there's 'Nightmare Moon's Return and Twilight's Dilemma' which shows how Twilight has to deal with Nightmare Moon coming back in a different form.