In the 13th century, the Mongol Empire led by Genghis Khan, rapidly expanded its territory. Goryeo (Ancient Korea) was no exception from its claws.

One of early clashes between the Mongolian army and the Goryeo army saw a resounding defeat for Goryeo, and in that defeat, a defeated general, who survived, walked into a forest at night to die and met a kumiho (nine-tailed fox)...