Camber of Culdi (The Legends of Camber of Culdi; V. 1)

Camber was the greatest of the Deryni who wanted to retire. But it was not to be. The kingdom of Gwynedd groaned under the tyranny of Imre and his sister and mistress, Ariella. And when Camber learned that Cinhil Haldane, a descendant of the previous kings, still lived, he was determined to set him on the throne in place of the evil ones....