The lead actor Bae Yong Joon was injured several times during the filming. First he was hit by an opposite actor's sword when performing the stunts. Then his neck and shoulder ligaments were injured severely when an actor during a wire action scene fell on top of him. Then Bae Yong-joon also injured his knee while landing. The drama had been supposed to be a dozen episodes longer but it had to be stopped because the actor had to treat his injuries.
The prologue plot is loosely based on the myth of the "Divine Regent" Hwanung who helped the bear to transform into a woman and married her.