The Aurelia Curse (Dragon Rider #3‪)‬

Dragons, myth, and magic unite in the third installment of Cornelia Funke's bestselling Dragon Rider series. Ben and the Greenblooms must protect a mythical new creature rising from the ocean -- a creature who can bring either light or darkness to whoever it first meets.

A new peril has emerged in the world of Fabulous Creatures. One that could cause the disappearance of their kind. Luckily, all of our favorite characters are back--Ben and Firedrake, his wonderful dragon friend, plucky Guinevere and the Greenbloom family, Sorrel the irrepressible brownie, the miniature man Twigleg and a host of new Fabulous Animals and sturdy helpers. But the threat is real and qucikly encroaching. A villian from the family's past is seeking revenge.

And all the while, the mysterious Aurelia, the most fabulous and powerful creature of all, moves across oceans to its final destination, introducing a new underwater world to enjoy.