The Chernagor Pirates — Harry Turtledove

Only a long-lost talisman can save a besieged kingdom torn between two kings, as a malevolent god marshals his minions to attack, corrupt, and destroy

Two lieges -- King Lanius, who is of royal blood, and King Grus, the usurper -- now share the throne of Avornis. The former wields no real power, kept impotent by the regents surrounding him. The latter mans the battle lines, determined to protect the kingdom from a fearsome, immortal god who was expelled from heaven. To the north, the city-state Chernagor is being torn asunder by a savage civil war that threatens to spill past the border at any moment. Catastrophe looms for Avornis and even two kings united may not be strong enough to save her. The kingdom's final hope lies in the recovery of the Scepter of Mercy, lost for four centuries. But the mighty talisman is in the hands of the Menteshe -- barbarian nomads who are vassals of the terrible exiled god -- and now that the Banished One wants to consume the entire world, they will never relinquish its power.
 
The Scepter of Mercy, Harry Turtledove's epic fantasy trilogy, continues with The Chernagor Pirates, the second volume in an adventure that pits man against man, and man against immortal. Originally penned under the pseudonym Dan Chernenko, it is an unforgettable tale that demonstrates the unparalleled creativity and unique storytelling prowess of the Hugo Awardâ€"winning master world-builder.