Onmyōji are practitioners of a traditional Japanese esoteric cosmology known as Onmyōdō, which combines elements of Shinto, Buddhism, and Chinese philosophy. They were historically responsible for various tasks, including divination, exorcism, and the management of spiritual affairs. In ancient Japan, Onmyōji served the imperial court and were often consulted for their expertise in astrology and the supernatural. They utilized tools like the I Ching and various rituals to maintain harmony and protect against malevolent spirits. Their influence can still be seen in modern Japanese culture, particularly in literature and media.