Onaj's Horn (The Silverskin Legacy Series)

As their adventures in Arylon continue, Ainsley, whose illness has left him with a pair of dragonwings attached to his shoulders, and Megan, who has the Pearl of Truth embedded in her chest, find they must defeat ever more powerful enemies before their true destinies are revealed. Before Megan and Ainsley return to Earth, they are pulled into another fantastic adventure in the magical land of Arylon. During a political summit, Evren Sandor, a mage with a questionable reputation, holds up a golden cone and announces that he is their new leader. Incredibly, the spell works! The source of Evren's power is a magical horn that once belonged to a unicorn named Onaj. Megan and Ainsley believe another unicorn's magic will be enough to counteract Evren's spell. With help from a ferret named Brighton and Sir Inish the dwarf, they seek out the White Order of unicorns. Their leader, Anala, agrees to help them destroy Onaj's horn. But when they confront the evil mage, Anala and Ainsley succumb to the horn's power. Megan must discover what it takes to break the spell—something she's had inside her all along—before it's too late.