In a world where ancient deities linger lurk the shadows, Boreum, a descendant of the Moon Goddess, is cast down to Earth from the Moon. She wakes up in a mystical lake on a mountain which is the domain of the long-lost goddess Mago, only to be accused for the Goddess' mysterious disappearance by her fierce believer Sanho.
Meanwhile, in the heart of Seoul's underworld, a mob boss dies under suspicious circumstances. At his funeral, a young shaman named Yeonhwa is caught channeling a false spirit. Boreum exorcises the malicious ghost and saves her, but Yeonhwa - powerless and in danger - begs for another god to possess her before her enemies realize she's lost her power. Moved, Boreum offers herself.
What begins as a reluctant alliance soon grow complicated as they become embroiled in a war between gods and demons. Boreum and Sanho discover that a dark spirit called Yosagwi is sacrificing women to power a growing evil. At the center of it all is Kim Hyun, Boreum's former lover, who conspired to drag Boreum to Earth and claim the moon's throne for themselves.