 It is based on the Korean folk tale "Prince Hodong and the Princess of Nakrang", which touches the story of the failed Nakrang Kingdom.According to the tale, there was a famous drum called the "jamyeonggo", literally "the drum that beats by itself," that possessed the mysterious power to automatically sound an alarm whenever enemies would invade its kingdom.The self-sounding drum caused neighboring nations, including the warrior state of Goguryeo, to hesitate about attacking Nakrang.