The Shadow of a Swan

Hi, this story is based on "Once Upon a Time" series.
We all saw how Emma won the battle against her evil side being cursed by power of the Dark One, but what if the weight of dark magic were unbearable for her and she lost control over it?...
Being lost in her own mind she will find some new things about herself and her feelings, but would it be enough for her to resist and remain herself?
Would it be the story about sacrificing or saving, or maybe both? And which role in all this fighting will have Regina?
How would her actions and words influence other characters and her life?
Does the Savior have the chance for a happy ending or does she only have one destiny-to be the Savior after all?