Plot twist or major disappointment?

I think your plot is great and it seems really fun. The only thing I would say is maybe come up with another situation for the curse? Perhaps it is very similar to a Netflix show called Once Upon a Time. The town people are cursed by the witch in the Snow White story and they can't leave nor can anyone come in.

 

It's hard to judge based on your outline. And that is because it will depend on how you write it.

A good description I have come across for twists (and endings) is "surprising but inevitable". You need to set it up throughout the story in the same way a mystery writer does with the murderer. You want the reader to figure it out the paragraph before it happens.

So, subtle Foreshadowing throughout the book and you will be fine. On the other hand, if it comes out of the blue, then readers will feel cheated.

 

Without seeing more, this falls into the baseline “it depends on how well you write it” which is very unhelpful. There are plot twists, and then there are holy crap plot twists. The latter is tricky, and I know I hit one once in Eve of Snows because that’s what my editor said on reading it, LOL, but it’s hard as hell to tell whether you succeed until you get reader reaction. Twists with reversals are even trickier.

For this particular setup... It seems like it’ll all be about how well you set it up and execute the events AND motivations.

 

Sounds like a good story to me.

 

I really like this idea. If you pull it off, I can see a lot of potential tragedy in making your savior think her mentor is the real bad guy. I wonder how that will end for them. Will her mentor be killed by the antagonist? Will they stand together in the end? Will they have to have a big long talk about how the mentor isn't actually the bad guy? And the growth it has the potential to force the protagonist to go through is amazing!

The only trouble is, how will you introduce your real antagonist? And how will you convince your protagonist that her mentor isn't the antagonist? People who are brought up their whole lives believing one thing can have a hard time changing their perceptions. For instance, if you are brought up your whole life believing that black cats are bad and your society enforces that belief you might actually turn and walk the other way if one crosses your path. Its just something to think about. Like Devor said, you have to create that sense of doubt about the dark savior.

 

The dark saviour needs a good reason to be helping Kara besides she read the script and found out she had to. She needs a good reason to believe that the way she's doing it is the right way. She needs to have a good reason to hide it from her, and she needs a good reason to reveal it.

Also make her and Kara kiss, which solves the "she needs a good reason to reveal it" issue.

 

There's always the second draft.

I plot (in my own fashion at least). But all the specific foreshadowing I put in my book was put in on the second draft. It's coming to the climax of the story and realising I solve the problem by doing X. When I go back for the second draft, I make sure to add in X at one or two points before the climax, or hint at it or place a red hearing for it. You can easily do the same here. The dark savior and the protagonish will clash a few times before they join forces (or whatever). When you get to the moment that they join forces and you find that they do so because the dark savior considers the protagonist ready, then you can go back to a couple of instances and show the protagonist not be ready and the dark savior react to it in some way.

 

I wouldn't worry too much about it if I were you. If it makes sense in your head, then you can make it work. Lots of settings don't make sense if you think about it too much.

On the face of it, mixing the lost roman legion with pokemon doesn't make sense, but Codex Alera became a bestseller based on this premise. Encapsulation a whole town in a dome makes little sense, but Under the dome did pretty well. I'm sure I can think of a few more if I must. The point is, write the story if you are exited about it. When you're done, read it (or ask other people for comments) and fix what needs fixing.

 

Provided 1. The two saviors dont kill each other and 2. There is a reason the second savior can enter (maybe she has strong enough magic to force her way in?) That can be explained I see no issue.