Bango knew how to control the dragon which is very strong and powerful ancient animal. The dragon was not harmful to human in the beginning but changed harshly by Bango. Moreover, since the dragon has lived for such a long period of time, it contains enormous power.
Bango had built the temple so that the dragon wouldn’t use its power against him, and he has placed the nail of dragon in the temple so that the energy of dragon could remain constantly. But after he fails the war of Tak-rok, he loses the control of the dragon. And the energy that has been kept in the nail started to spread out. That energy made other organisms to mutate into horrible creature, and they started to destroy the nature.
Hanin had ordered to destroy all the nails of dragon that are placed all over the nation and most of them were destroyed. Magicians of son of the sky were always looking out for them so that wicked power wouldn’t reach the Geum-Oh Mountain. One day, while they were searching, they found that wicked power. Son of the sky dispatches an observer group, and the group has found the island called E-Mok Island which already had rumors that lots of mutated dragons were living. As a result of inspection, there were 4 nails of the dragon deep inside of the island, in the center there was a temple of the dragon remaining. They tried to destroy the nails of dragon, but due to the attack of mutated dragons, E-Moogies, they had to take back. The island was already under control of E-Moogies and Demon soldiers. And what is worse, it was too far away from the Geum-oh Mountain, so the power of son of the sky wasn’t able to reach there. So, son of the sky decides to gather a troop from all over the nation so that he can destroy every nails of dragon.