The Heart of the Moon

"The Isle is supernatural and may produce anything. It is a place half in this world and half elsewhere. In spots, they say, it opens on the country of the moon itself. Therefore, anticipate magic, and great danger. Sacrifice is common on the Isle. So is death." Clirando, a celebrated warrior, believes herself to be cursed. Betrayed by people she trusted, she unleashes a vicious retaliation upon them and then lives in fear of fateful retribution for her act of cold-blooded vengeance.  Once every seventeen years, the full moon of midsummer shines for seven nights, and celebrations take place upon the mysterious Moon Isle.
When Clirando is ordered by the priestess of the temple of Parna to travel with seven companions to the festival on the Isle, she sees this as her punishment at last - if not her doom. But the Isle is mysterious and disorientating. The senses cannot be trusted. Strange visions haunt the shadows. Perhaps the dead walk there. During the nights of the full moon, anything might happen. Set in a land resembling Ancient Greece, in this novella Tanith Lee explores the dark corners of the heart and soul within a vivid mythical adventure.
The book also includes 'The Dry Season' another of her tales set in an imaginary ancient world of the Classical era.