An onmyoji was a master of onmyodo, the way of yin and yang, the Japanese court art of divination, calendar-making, astrology and the aversion of misfortune.
The court specialist
The onmyoji served the imperial court as the specialist in a body of cosmological and divinatory technique derived from Chinese sources, the reckoning of the calendar and the auspicious and inauspicious days, the interpretation of omens and celestial events, divination, and the ritual aversion of the misfortunes and malign influences that the system identified, so the office joined the practical work of calendar and astronomy to the ritual management of unseen dangers. At the height of the tradition the onmyoji held a recognised place in the machinery of the court, organised in a dedicated bureau.
History and afterlife
The art was at its most influential in the Heian court, and its greatest practitioner, Abe no Seimei, became a legendary figure around whom many tales gathered, so the onmyoji passed from history into a rich folklore of the master who commands spirits and reads the hidden order of things. As a formal court institution the tradition declined in later centuries and was eventually abolished in the modern reorganisation of the state, but the figure has enjoyed a vigorous afterlife in Japanese literature, drama and popular culture. The onmyoji thus represents a distinctively Japanese synthesis of imported Chinese cosmology and local practice, the court diviner and ritualist who managed the calendar and the unseen forces on behalf of the state.