River of Blood

From the publisher:

For generations beyond counting, the River Purvaas has known the pain and suffering of war. As the key border between three perpetually feuding kingdoms, so many battles have been fought over its bridges and fords and on both of its banks that all sides have lost count. But now a new horror rises to haunt the banks of the Purvaas. The dead rise to haunt those who waged the wars that slew them!