The Antyre Chronicles, book 2 : Kings and Assassins
Lane Robins2009

Controlled by an aristocracy whose depraved whims bow to neither law nor god, the kingdom of Antyre is under siege from the only man who can save it. He is Janus Ixion, the new Earl of Last, a man whose matchless fighting abilities and leadership strike terror in Antyre's powerful noble houses.

For Janus is the illegitimate son who has returned from the brutal slums to reclaim his birthright, and will go to any lengths to become king and reverse his country's decline. But with a conquering foreign prince sowing chaos throughout the kingdom, Janus must battle the terrifying power of Antyre's forgotten god, one who has gifted Janus's vengeful wife with mysterious and dangerous skills. As Antyre nears irrevocable collapse, Janus's manipulations and all-consuming ambition will force him and his country to choose between the rule of resurgent gods, or a victor's throne of ashes.