According to Heki, the sword is the strongest weapon in the world that has emerged through 500 years of warfare. Of the numerous weapons invented over the past 500 years the sword is the only one that has evolved and been refined with the purpose of defeating enemies. And there is no one that cannot be defeated by a sword. It all comes down to who wields it. That the essence of the sword.
According to the teachings of the Clan Shiyuu the sword did not originate as a tool of warfare for the killing of men. But rather it was born as divine instrument for the purpose of venerating the heavens. The god-fearing people would pay homage to the heavens by holding a "priestess dance" where the priestess, host to the gods, would dance a midst a sea of flames and offerings. But as time went on, people began to fear the strength of man rather than the heavens which caused the Shiyuu clan to fade into darkness where they changed into something frightening.