Magic

In the center of Luster towers an enormous tree that is the Heart of the World. Now the tree is wounded, pierced by a tunnel that connects it to Earth. Through that tunnel strides Beloved, the ancient enemy of the unicorns, followed by an army of Hunters eager to destroy every last unicorn.

Luster, the world where the unicorns fled to escape the Hunters who have sworn to wipe them out, has dangers of its own - as Cara discovers when she attempts to cross that world in a desperate effort to rescue her grandmother.