Samuel R. Delany 
Jewels Of Aptor 

When Argo, the White Goddess, orders it Geo, the itinerant poet, and his three disparate companions journey to the island of Aptor to seize a jewel from the dark god, Hama, and return it to Argo so that she may defeat the malign forces ranged against her and the land of Leptar. But, as the four push deep into the enigmatic heart of Aptor and the easy distinctions between good and evil start to blur, their mission no longer seems straightforward. For Argo already controls two of the precious stones and possession of the third would make her power absolute. And the four friends have learned that power tends to corrupt…