The theme of prophecy in the stories of Greek heroes primarily underscores destiny's influence on human action. Prophecies often forewarn heroes about their futures, prompting them to confront their fates, which can lead to both triumph and tragedy. Such narratives illustrate the tension between free will and predetermined outcomes, offering rich explorations of character motivation and moral choices. These prophetic elements contribute to the development of Greek tragedy, emphasizing the inevitability of fate while inviting questions about human agency and the search for identity amid external pressures.