Heart of Midnight — J. Robert King

Revenge. The word rings in Casimir's mind. He has laid his plans for a decade--ten years among the scruffy children, the rats and the fleas of an orphanage. At last Casimir sets his intricate scheme into motion, seeking glorious revenge upon the man who slew his mother and made him an orphan.

But revenge is a merciless master. To slay his nemesis, Casimir summons a dark and powerful curse. And when that terrible curse is summoned, he must confront the greatest foe of all . . . himself.