During the latter part of the 14th century, King Taejong abolished the Goryeo Dynasty in order to establish the Kingdom of Joseon. Some were aware of the deal he made with an evil spirit — which in turn used their power to possess humans who would control and terrorize the world. The king’s sons, Princes Chung Nyung and Yang Nyeong, are his main opposition, each with a different reason for standing inhis way.
(Source: DramaWiki)
~~ The series was cancelled after two episodes.