Twilight didn't want to use dark magic. She had seen what had happened to the last user of it. But she had to. The Crystal Empire was in danger, and it was the only way to get to it's heart.
About a year later, Twilight is plagued with nightmares. Tempting her to give in to the corruption. To join King Sombra. Will she prevail? Or will she fall? And what effect will it have on her friends?
Diverges from Canon after Season 4.