Uh… what? Seriously, I am lost. The conversation between Evening Star and Luna goes over my head, especially when Star’s the one to discount… well, the stars. No idea what that question is supposed to mean, especially given how she’s supposed to be encouraging Luna that she still serves a purpose. And the ending… What?

Sorry, but you completely lost me with this one. I have no idea what you were going for, and as such now idea how to fix it.

>>FanOfMostEverything

I assumed that that was a mistaken break in the dialogue and that it was Luna discounting the effect of the stars.

For the rest of it, I believe we're in the time-honored genre of 'the twist is that the fic is actually set a thousand years ago'. Er, not to denigrate that per se. There's nothing wrong with trying your hand at an idea that's been done before. Writing is all in the execution.

I think the idea here is a little stronger than the execution. There's some technical issues with the dialogue and it could stand a good copy-editing, I think there are a few minor grammatical errors. (I spotted at least one past tense/present tense problem, and a few lines just seem awkward and clunky.) I do think it does a good job of conveying the mood and feeling of Celestia and Luna, how they feel, how they misunderstand each other.

Celestia smiled with the corners of her mouth.

I know what you were going for, but when I read this, I couldn't help but try to figure out how to smile with just the middle of your mouth.

Anyway, just as SPark mentioned, I think you did a good job when conveying the feel of the scenes in a subdued way. There's no outright stating of emotions, but you can get a grasp on the mood of the characters. So kudos for that.

Onto the negatives, well... The story feels rushed, there's no other way of putting it. We get a nice scene with a melancholic Luna, a quick snippet of Evening Star talking to Celestia, then boom, Nightmare Moon. That really pulled me out of the story.

As far as origin stories, your concept was good, but a bit of focuse could have helped this story shine.

Celestia smiled with the corners of her mouth.

Same as Zaid. When you're obliged to write in such cramped a space, going for pleonasms isn't the brightest idea…

"Indeed, even you prefer the day." Luna looked away. "I wonder if I'm needed anymore. I haven't been needed since Discord."

"What good are the stars when they have no effect on ponies' lives?"

"They don't? Are you sure about that?"

Something's missing here. Either the two first lines must be joined, because it’s Luna's words in both, or you’re missing a reply. I understand why others have become lost. It’s the same two or three lines after.

Hmmm… I think Celestia is too unconcerned here. She wouldn’t design a surrogate for dealing in that matter.

In all, I don’t know what to think. The arc is pretty weak. The first scene barely adds anything to the story, which feels somewhat rushed. I think, much like FoME, that it’ll a major overhaul to be really effective.

Genre: A Hero Falls

Thoughts: For me, the story didn't really start until this line:

"I could never be like my sister."

Everything before that felt vestigial, and unfortunately the lines right after it suffered from a confusing lack of attribution. Also the middle chunk felt unnecessary. Or maybe you could move it to the beginning, and have Evening Star say that she's planning to talk to Luna, instead of already having done it? That could be a good setup.

I was OK with the twist, and I think it's interesting to see Luna's downfall come more from a feeling of uselessness than what I'd usually expect. Also, I think the batpony had the funniest and strongest bits, and I think there's some good emotional resonance to having her be a triggering cause for Luna to turn. If anything, I'd say give the batpony more lines and focus and see where it goes!

Tier: Needs Work

Others already pointed out the technical problems, so I'll skip those. My problem is this doesn't sound like Luna. First, she was shown as having an old-english type of accent after her return, and that's absent here. The introspection here also feels forced, rather than flowing naturally as thoughts do.

Another thing that's odd: Evening Star is actually the star of the story. She has personality, and is obviously on casual terms with Luna. That's something that caught my interest far more than where I knew the story was going (that is, Luna's Fall.) Show me more of her, how that came to be, where she goes during the day! That hooked me!

Celestia smiled with the corners of her mouth.

...as opposed to...?

A softer, more subdued take on the fall of Princess Luna. Nightmare Moon begins, not with a bang, but some folksy, charming dialogue by a cute batpony.

>>Monokeras

Hmmm… I think Celestia is too unconcerned here. She wouldn’t design a surrogate for dealing in that matter.

I like this a lot, actually. Gives some depth to their relationship by showing how lacking in depth it really was. Suggests that Celly could probably have avoided Luna going Lunatic if she'd played a more direct role in her life.