The Unknown (The Sorcerers' Prophecy Book 1‪)‬

Casey and Kate are just average teenagers when their reality is shattered with the discovery of their real home, Alagia. In this alternate, magical world, the girls learn of a prophecy that says the two will split into the sides of good and evil, and in order for Alagia to maintain peace, only one of them can survive their imminent battle. The only problem is that no one knows if it is Casey or Kate who will turn evil and help the dark sorcerers of the land. The girls struggle to face their new reality, especially since Casey and Kate are twin sisters.