Sea of ghosts - Alan Campbell

When the last of the Gravediggers, an elite imperial infiltration unit, are disbanded and hunted down by the emperor they once served, munitions expert Colonel Thomas Granger takes refuge in the unlikeliest of places. He becomes a jailer in Ethugra - a prison city of poison-flooded streets and gaols in which a million enemies of the empire are held captive. But when Granger takes possession of two new prisoners, he realises that he can't escape his past so readily.

Ianthe is a young girl with an extraordinary psychic talent. A gift that makes her unique in a world held to ransom by the powerful Haurstaf - the sisterhood of telepaths who are all that stand between the Empire and the threat of the Unmer, the powerful civilization of entropic sorcerers and dragon-mounted warriors. In this war-torn land, she promises to make Granger an extremely wealthy man, if he can only keep her safe from harm.

This is what Granger is best at. But when other factions learn about Ianthe's unique ability, even Granger's skills of warfare are tested to their limits. While, Ianthe struggles to control the powers that are growing in ways no-one thought were possible. Another threat is surfacing: out there, beyond the bitter seas, an old and familiar enemy is rising - one who, if not stopped, will drown the world and all of humanity with it . .