Onmyōji are practitioners of a traditional Japanese esoteric cosmology known as Onmyōdō, which combines elements of Buddhism, Shinto, and Taoism. Historically, they served as advisors to the imperial court, using their knowledge of astrology, divination, and natural phenomena to guide decisions and ward off evil spirits. The role of an Onmyōji included performing rituals, casting spells, and interpreting omens. They were often associated with the use of talismans and protective charms. Famous figures like Abe no Seimei exemplify the mystique and influence of Onmyōji in Japanese folklore and culture.