Shugendō

Shugendō is the practice of shinobi asceticism-shamanism incorporating ambient physical energies into the light and dark techniques of the ninja in order to drastically amplify his offensive and defensive capabilities. Born in the times of the Sage of the Six Paths, this ancient highly syncretic mystical-spiritual discipline evolved as a response to the pacification of the war torn tribes by Kaguya Ōtsutsuki.

History
Kaguya Ōtsutsuki partook of the sacred millennial fruit of the Shinju tree and ascended to good hood. Granted the power of the kami, Ōtsutsuki pacified the warring tribes under her benevolent rule. She bore a son, also gifted with godlike power, that would go on to spread the his ideals and religion, the Shinobi Sect (忍宗, Ninshū), which eventually came to be known as ninjutsu. However, disgruntled heretical sects dissatisfied with the external pacification took up the arts of the sage and modified them according to disparate ancient practices of nature mysticism.

Sometime after the advent of Ninshū, a mountain shinobi-shaman, En no Gyōja (役行者?, lit. "the Ascetic from the En clan") gathered together divergent disciplines of the Yamabushi of his time. He was the only one to recognize the underlying pattern running through varying disciplines and utilized these commonalities in the founding of Shugendō. Unlike Rikkudo Sennin, Gyōja confined his emerging discipline to only the most talented disciples of like mind. As a child he had been orphaned by the tribal wars. Despite these devastating circumstances, as a child he found himself horrified by the overwhelming power of Ōtsutsuki and her offspring. Even the practitioners of Ninshū were as dust in a hurricane before them.

Having studied Ninshū, he sojourned across the globe, searching for a path to augment the comparatively meager capabilities of those who would one day be ninjas. Stumbling upon the Yamabushi, one by one he added their arts to his own and founded a single discipline capable of taking advantage of any form of ambient physical energy in order to augment the shinobi's energy. His ancient discipline has passed down from Shugenja to disciple to modern times. Orochimaru himself attempted to ascertain the true nature of this hidden discipline, yet failed and moved on to more accessible pastures.

Origin
Atmospheric electricity exists as daily electromagnetic fluctuations associated with the Earth's atmospheric electromagnetic network embedded throughout those layer of gases surrounding the planet.

The regular locomotion of electric current within the Earth's crust, atmospheric layers, and especially the ionosphere comprise the global atmospheric electrical circuit. Shinobi researchers consider this circuit of flowing electricity analogous to the chakra pathway system of a human being. Experiments demonstrate that the intensity of extremely dense charges form a graduated electric field. This electric field gradient reaches into the upper atmosphere whereupon the voltage increases to a maximum of 300,000 volts per foot at an altitude of approximately 30–50 km above the Earth's surface.

Add to this the interplay of other common forms of energy such as kinetic motion, electromagnetic radiation, as well as, various kinds of potential energy, i.e. gravitational and elastic and one arrives at the basis for the continuous massive transformation of one form of ambient physical energy to another, both separate and distinct from the "natural energy" utilized by sages. Extending the earlier metaphor of the chakra network, one could consider these forms of ambient energies as analogous to the physical energies found in the cellular matrix of the body, while the sages' "natural energy" might be considered the spiritual energy of the planet itself.

Full understanding of these disparate realms of energetic phenomena requires the knowledge of several disciplines beyond ninjutsu or even senjutsu. The collection of these disciplines comprise the body of knowledge known only as Shugendō (修験道). Shinobi who practice this art form are referred to as Shugenja or mountaineering ascetic/shaman. The original practitioners of precursors to this art in the era of the Sage of the Six Paths were known as yamabushi, also known as "mountain monks." These mountain monks practiced an early form of Shugendo, shinbutsu shūgō, "The Gathering of Gods and Buddhas" that sought to capture the energies of the heavens and harness them for the use of mankind. This early art form eventually evolved into Shugendō, the tactical use of all ambient physical energies.

Execution
The Shugenja utilize a form of In'yōton or Yin–Yang Release to take control of ambient physical energies. The user develops yin chakra on the left side of the body and yang on the right or vice versa depending on neurological dominance. (For instance, electrical energy drawn directly from the ionosphere.) This process resembles Sasuke Uchiha's Kirin technique in that 1) a small amount of Yin-Yang chakra controls a massive quantity of ambient physical energy and 2) techniques take on a wildly exaggerated scope and scale beyond those of shinobi or even sages. However, it does not require the same massive amounts of preparation. Any form of ambient physical energy can be used. The effects however, vary depending upon which kind of energy is adapted. Unlike the sage, to master Shugendō the ascetic requires only advanced chakra control on the level of the Hyuuga or medical ninja capable of using Byakugo, rather than massive amounts of stamina. For this reason, it remains impossible for most shinobi to judge the power level or the stamina of even average Shugenja. Useful categories of energy include, but are not limited to: Acoustic, Seismic, Radiant/Electromagnetic, Chemical/Combustion, Mechanical/Kinesthetic, Gravitational/Tectonic, etc. From these disparate types of energies the Shugenja develops various enhancements in offensive and defensive applications, as well as, bodily augmentation. Also unlike either the shinobi or the sage, a Shugenja's techniques remain immune to most kinds of chakra absorption, as they are primarily comprised of real physical energy.

Risk
During any type of physical augmentation, the Shugenja must literally use his own chakra to buffer his body from interaction with these energies. Failure to do so may result in destruction of the physical form. Large scale AoE attacks must remain tightly controlled for the same reason. Disciples find themselves particularly susceptible to such vagaries and therefore suffer from an even larger attrition rate than toad sage acolytes, making this discipline one of the most difficult art forms to learn.