The Jewels of Aptor
Samuel R. Delany
 In a post-atomic future, when civilization has regressed to something near the Middle Ages, or even before, a young student and poet, Geo, takes a job as a sailor on a boat with a strange passenger, a priestess of the goddess Argo, who is heading toward a mysterious land of mutants and high radiation, called Aptor, presumably to recapture a young priestess of Argo, her daughter, who has been kidnapped by the forces of the dark god Hama.