Heat of the Lava Dragon: A Branches Book (Dragon Masters #18): Volume 18

Drake's friends Mina and Caspar, their dragons, and Worm were trapped in stone by the evil wizard Astrid who has stolen their dragons' powers, but Drake himself was saved from a similar fate by Astrid's sister Hulda. Now because of his strong connection with Worm, Drake's able to help his dragon to break free, but to free the others they need the assistance of three other dragons--a lava dragon, a sea dragon, and a wind dragon--and they have to do it before Astrid can steal the powers of even more dragons.