Scholastic Inc. The Whispering Oak: A Branches Book (the Last Firehawk #3)

ONLY THE BRIGHTEST MAGIC CAN BEAT THE SHADOW. Thorn's dark magic continues to spread across Perodia. Tag, Skyla, and Blaze must hurry to find the next piece of the Ember Stone! But this will be a long journey. Tag and his friends will have to cross the tornado-filled Shifting Sands to reach the Whispering Oak. Will they find the stone in time? Or will Thorn's spies beat them to it?