Crusade - Anselm Audley

Cathan has discovered powers within himself since his story - and that of the waterworld, Aquasilva - began in HERESY. He has also found that he is the Emperor Orosius's brother - but Orosius is dead, and Eshar is now set in his place, thanks to the Imperial Navy's king-making. Meanwhile, the religious fanatics of the Domain continue to seek out heresy - and Cathan in particular.
Still refusing to attempt to place himself on the Imperial throne, Cathan studies the history of storms and the terrible effects of previous meddling with Aquasilva's weather systems. But the Domain's dogs are everywhere, and capture lays in wait for him...and with it, the discovery of his true identity, and death.
CRUSADE completes the AQUASILVA trilogy, which has seen the young Cathan come of age, in more ways than one. In its deep politics, world-building and characterisation, it is a masterpiece of fantasy fiction from a new star.