Angra Mainyu, also known as Ahriman, is the destructive spirit in Zoroastrianism, representing chaos and evil in contrast to Ahura Mazda, the supreme god of light and goodness. This duality is a core aspect of Zoroastrian beliefs, highlighting the eternal struggle between good and evil that defined much of Persian religious thought and culture during the era of the Persian Empire, as well as influencing later societies like the Byzantine Empire.