Yamabushi were mountain monks who lived in the closest places on earth to the heavens. They sought to augment their human capacity by taking control of the various energies found in nature. They developed techniques designed to increase the chakra control of the user to the point where he became capable of easily controlling these massive energies with his own chakra thereby supplementing his own energy with that of the outside world far beyond what a normal shinobi is capable of producing. These techniques were further refined by En no Gyōja during the founding of Shugendō and are still in use today in the Land of Whispering Bone.