The King's Priest - The Four Masters Series, #1

The year is 971 AD. Ireland is riven by internal conflict and the target of expansionist Viking ambition. In the aftermath of a bloody battle, an unusual priest stands against the chaos. Rannal must deny his savage past to unite Connacht and defeat the invaders. His actions rekindle a fellowship but pit him against a forgotten spectre from his former life. The essence of the fabled Queen Medb is embodied in the characters who must rise to the challenge of salvaging a future from the pyre of a ravaged land. Centuries-long rivalries are renewed in a storm of events that echo the ancient sagas.
Celtic and Norse cultures clash at the frontier of the Viking Empire, and the names of heroes will emerge to be proudly born by their descendants for a thousand years.