"The Deryni" is a fantasy novel by Katherine Kurtz, first published in 1970. It is set in the fictional medieval kingdom of Gwynedd, where a group of people known as the Deryni possess magical abilities. The story explores themes of power, prejudice, and the struggle for acceptance as the Deryni face discrimination from the non-magical population. The novel follows the life of Kelson Haldane, a young prince who must navigate political intrigue and the challenges of ruling a kingdom divided by fear of the Deryni. As he learns about his own heritage, Kelson seeks to unite his people and protect the Deryni from persecution.