The Great Seer is set during the reign of King Gong Min and centers on the power struggles behind Korea's historical transition from the Goryeo to the Joseon dynasty. Though it features seers, geomancers, and diviners, the drama focuses more on political intrigue than fantasy.

Mok Ji Sang, a gifted geomancer with the ability to see into people's pasts and futures, is misunderstood by many who believe he’s possessed by dark forces. Despite suspicion and opposition, he rises to become a powerful "king-maker," ultimately aligning with General Yi and playing a pivotal role in reshaping the future of the nation.