Luna has the ability to contact those who are dead, but haven't chosen to move on from their death. For ponies that try to make others lives feel great she gives them a choice for if they want to stay and help, or leave and see what is beyond them. Eventually leading to extreme amounts of stress creating the mare know as Nightmare Moon.

Edit:
For those reading/starting to read: I don't update often, because I'm studying to become a software engineer. I don't have much time to write, or even to have "fun" at all. I'd appreciate your patience, and thank you. :D

A new darkness is spreading over Equestria, and they six Rainbow Dash, Fluttershy, Applejack, Pinkie Pie, Rarity, and Twilight need to find a way to stop it. They find new sorts of magical objects that are powerful beyond their knowledge. Relationships grow apart, and closer together.

Edit:
Story is finished, but not edited. I promise eventually I will get to editing it all, but for now I have other projects to do. Yes I have started another story, but that is only for times in which I feel inspired to write something dark, in here I have a lot of editing to do, and I've started to edit the first chapter and make some small short plot changes.