This is a tale inspired by the animation "Children of the Night" by Duo Cartoonist via YouTube and by how the author had first interpreted the video. Nightmare Moon and Princess Luna's banishment are not canon in this story.
Ever since Discord was defeated and turned to stone, the two brave Princess sisters, Celestia and Luna have ruled Equestria. And they have been working on rebuilding Equestria to its natural state with all their might. But one thing had caught Luna's eye and had escaped Celestia's notice: how certain children were treated and leading miserable lives.
Somehow managing a negotiation with her sister, Luna gathers the children and leads them to a far off land, still within the bounds of Equestria. When they settle, Princess Luna promises the foals and new, prosperous colony which will ensure the strength and happiness of ponykind. And what can go wrong with that? Lots more than expected. Can Princess Luna safely protect her Children of the Night?