The Heavenly Emperor divided the sky into the northern, southern, eastern, and western quadrants, each with seven star houses and each ruled by a divine beast.
In this system, there are 28 star houses (that is to say, constellations) which run the circumference of the sky. The Four Gods are the central figures of an ancient Chinese system of astrology and geomancy which was imported to Korea and Japan and absorbed into Onmyōdō mysticism, among other beliefs.
