Captain's Fury (Codex Alera, Book 4)

The author has created a world in which the elemental forces of nature take physical form and are used for protection. Now, as enemies become allies, and friends become foes, a danger beyond reckoning looms for all. Tavi of Calderon realizes that a peril far greater than the Canim exists. Tavi proposes attempting an alliance with the Canim against their common foe, but his warnings go unheeded. For the Senate's newly appinted military commander has long desired to wipe out the Canim 'scourge' and their slave allies. Now Tavi must find a way to overcome centuries-old animosities if an alliance is to be foged, and he must lead his Legion in defiance of the law, against friend and foe - or none will have a chance of survival.