Twilight Sparkle has always bargained for things. Whether it be books, or pleas for help. But this time, there really is such such thing as "getting more then you bargained for." When Twilight had attempted to dig into King Sombra's past, somehow, he had just enough of his soul left to enter Twilight's mind. Now feelings Twilight shows toward her friends are cold and distant, and she wants to take over the world. Because she knows the existence of Sombra, she thinks he is making her feel these things.
Or were they awakened?