Geartree The Airdrianium Adventures Book Two

A year has passed since a dragon declared Anderax Grayvenhorn, a dragonrider, and Peacecrafter. Yet, they still can't find any new sources of airdrainium - an ore that lifts cities into the sky. Now he attends the Highland Dragon Academy and can climb trees every day. However, Anderax isn't certain he can live up to this new title, or avoid the fear taking hold of everyone's hearts. When dragonriders go missing, he and his fellow cadets return to the aircities. They discover an iron-bound book that leads them on a quest to an ancient city in the clouds, as a mysterious new enemy darkens the horizon. Geartree is the sequel to Steamtree: The Airdrainium Adventures