I was wondering if there were any fics where Sunset, instead of fighting Twilight, basically tries to subvert her from her mission. Maybe something like when she confronts Twilight in the hallway early on, she goes all 'Celestia has been manipulating you from Day One you poor fool, notice how she never told you about Nightmare Moon? Or how she let you fight an evil dictator from a thousand years ago with absolutely no back-up? Or how she sent you an incomplete spell that would screw up your friends Cutie Marks, and made you a Princess right after you 'fixed' it? I ran away because of her, you know.'

(This assumes she has knowledge of events happening in Equestria, not too far-fetched considering her ability to go through the mirror portal and know exactly where Twilight's room is, along with roughly what the Element of Magic looks like)

If there isn't anything like that, I think it could make a cool premise. I don't think I've actually seen something where Sunset finds out about Nightmare Moon prior to running away either, and feeling like Celestia was setting her up. So in the above scenario, I guess Sunset could also actually mean the words, and in an extremely twisted sense deliberately be against making friends since she thinks Celestia would use potential friendships in some sort of grand scheme.

An interesting concept, but there's something that makes it really hard: Would Twilight believe in Sunset?

All Twilight knows when she first crosses the portal is that Sunset is a corrupted ex-student. Why would she trust when Sunset claims that Celestia is evil?

It would take either one very long chapter, or several ones, for Twilight to start believing in Sunset...

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That's not a bad idea at all. I'd read it,

4875760 I haven't thought too hard about it, and if I were to even take a stab at it myself I would definitely put in a lot more thought to the events, but a couple of other points did come to mind when reading your post:

First, as far as we know, Twilight only finds out about Sunset's existence as Celestia's former student right before she goes through the portal. Sunset was created for the movie of course, but Twilight doesn't show the slightest sign of knowing about Sunset prior to the start of the film. Something like a 'Did Celestia even tell you about me? Of course not, I slipped free from her reigns', basically a combination of trying to say Celestia isn't a perfectly benevolent ruler, as well as trying to hint her as a controlling pony who keeps secrets

Second, there IS the matter of Principal Celestia. Sunset has to know she's the Princess' counterpart, obviously. Feasibly she could somehow set Principal Celestia up to make a bad first impression on Twilight, who might think counterparts are alike and if that's how Principal Celestia acts, is Princess Celestia's personality all an act?

(Though in my original post, I wasn't trying to imply Sunset saying Celestia was EVIL or anything, just that she was a grand manipulator who likes to push ponies into doing things and hides pretty big damn secrets)

It's an interesting idea. I think for it to work Sunset would have to have proof as well as evidence of something Twilight doesn't know about at all. Not sure what that would be, and Twilight would still probably try to believe in her teacher and friend at first so it would need several chapters before it happens. I'd give it a read.

Trust me, I've looked for a story like that for literally a year. So far no luck. If your planning on writing one I do have an idea though. Have a type of conflict between Celestia and Twilight that is earily similar to an argument between Celestia and Sunset, then have sunset shimmer arriving a little early and have her eavesdrop on the argument. Make Celestia go a little too far when she says something very personal that immediately ends the argument. Then everything goes as did in the movie with Sunset Shimmer stealing the crown and Twilight going after her. Then do what you said make Sunset bring up the fact about Nightmare Moon, Sombra and then finally the argument that Celestia and Twilight had, and if you have to bring up how similar Twilight and Sunset are (which is why I think that this story could work personally). And there you go (btw if please make it a pairing as well). The only problem I don't know what you could use for the personal argument between Celestia and Twilight. The reason I'm giving this idea to you or anyone who wishing to write a story like this is because I can't write for shit.

Sounds like an interesting premises.

Actually, I think it would work better if you did have Sunset believe her words. It that version, it's possible Sunset didn't dabble in "forbidden knowledge" and defy Celestia just for "power" and "authority" but for the power to (finally) be able to control her own life. Still leaves her as the antagonist of the story, but she has a freudian excuse and it gives Twilight the chance to try and "counter-corrupt" Sunset (by showing her that Celestia was not what Sunset believed her to be) if you want to go that route.

Well, that's definitely an interesting premise, but you kinda have to figure out where it leads. I would definitely have trouble building up a good punchline to that beginning, at least not one that would lead to evil team-up, and those never work out well in literature in my experience.

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I've had a day to think this over. Since I guess there isn't any story like this published out there, this moves into solid idea territory. I'm not necessarily saying I would write it myself, but here are my two bits on what I would do if I did. I enjoy reading ideas, so throw in your own thoughts as well if you'd like.

I personally think it does work better if Sunset actually believes her own words, believes that Celestia was setting her up for something the whole time. If that's the case though, I think that at the same time she pulls her alpha bitch act while trying to claim the crown for her own, Sunset also tries to help Twilight in some manners, like getting her a place to stay or helping her adapt to human culture, giving her a nuanced character.

Now, Sunset plausibly can know of the general events that occurred in Equestria during the time she was away. However, the one thing I think she could use to really make Twilight question Celestia's actions is also the thing she's least likely to know about - specifically, Chrysalis posing as Cadance. Twilight's blow-up was in relative private, and I don't think too many knew even Celestia brushed Twilight's concerns off. It may be more plausible instead for something to occur to remind Twilight of it herself.

I mentioned the use of Principal Celestia before. Sunset already can say "She let you be a student here with absolutely no ID or documents whatsoever" and play her off as not caring too much about the safety of her actual students or something, then go on about how counterparts have similar personalities. Twilight will see that to be pretty true with the Humane Five. Perhaps Sunset sets it up so Twilight comes to Celestia with a concern only to be brushed off, or maybe make it so that it's Celestia disciplining Twilight over the gym being trashed instead of Luna. Flash will still rescue her, but Twilight's confidence in Celestia could be shaken. Perhaps something Principal Celestia said or did a long time ago when Sunset first attended CHS further cements Sunset's opinion that the Celestias can't be trusted.

To an extent, it would be easier to write this by making the portal open for longer than 3 nights, so a writer doesn't have to shove all this action into the time span of two days. I suppose the logical end of this would be that Sunset doesn't turn into a she-demon but something more representative of her twisted beliefs, and Twilight and co can't just use magical harmonious purifying beam followed off by some words. I can't even tell if I would want a 'happy' ending where Sunset and Celestia make up, or a more bittersweet ending where Twilight gets her crown back but can't quite convince herself Sunset is wrong.

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Nice ideas
The bittersweet ending would be better as it could set up a sequel.