Avatar: The Shadow of Kyoshi by F.C. Yee

A New York Times bestseller, Avatar, the Last Airbender: The Shadow of Kyoshi is the second in the Chronicles of the Avatar duology, the epic, can’t-miss follow-up to Avatar, the Last Airbender: The Rise of Kyoshi.
 
Kyoshi’s place as the true Avatar has finally been cemented—but at a heavy cost. With her mentors gone, Kyoshi voyages across the Four Nations, struggling to keep the peace.

But while her reputation grows, a mysterious threat emerges from the Spirit World. To stop it, Kyoshi, Rangi, and their reluctant allies must join forces before the Four Nations are destroyed irreparably.

This thrilling follow-up continues Avatar Kyoshi’s journey from a girl of humble origins to the merciless pursuer of justice still feared and admired centuries after becoming the Avatar.