2500 years ago, there were 2 mysterious beings that tormented humans. These beings were locked up in 2 caskets by a formidable power, and in order for them to assume their form, they must infiltrate 7 vulnerable human hosts. Centuries later, Monk Ha-jung, the protector of one of the caskets, realizes that one of the beings has reawaken and orders his fellow monk Chung-seok to seek Jin-soo, who was born to stop these beings. Knowing fully well what this being is capable of, Jin-soo begins the hunt to find the being with Chung-seok in order to stop it once and for all.