Book of Doom (Diadem Series)

Now that one of the Three Who Rule has escaped, the Diadem is in serious danger. Nantor, Pixel's ancient, evil self, has taken over the young magic user's body and is threatening to, once again, rule the worlds. Poor Pixel is alive in a small cell of his mind, but Nantor's strong spirit will soon engulf him. It's up to Score and Helaine to stop the powerful Nantor, but how? Score has been banished to a dangerous land of killer plants. And Helaine is trapped on Calomir by the Overmind who has implanted a microchip in her head. Even Jenna has been separated from the other young magicians. Are Pixel, Helaine, and Score doomed to become the heartless, evil rulers of an enslaved Diadem?