Shugendō reveres En no Gyōja (also En no Ozunu) as its founder. Toward the end of the seventh century, he secluded himself on Mount Katsuragi in Yamato, a practitioner known for the power of his spells.

The En no Gyōja handed down to us is scarcely a human figure. He is said to have commanded demon-spirits at will, to have kept two demons, Zenki and Goki, at his service, and even to have bound Hitokotonushi, the deity of Katsuragi, with a spell. These are the tales told in the Nihon ryōiki, a collection of setsuwa stories from the early Heian period, and in the temple legends of later ages. In 1799 (Kansei 11), well into the Edo period, Emperor Kōkaku even bestowed on him the title "Jinben Daibosatsu" (Great Bodhisattva of Wondrous Working). Over the course of more than a thousand years, the figure of En no Gyōja has been drawn ever larger, little by little.

And yet what survives as solid historical fact is a single record: one short passage in the official history Shoku Nihongi, under the third year of Emperor Monmu (699). What it records is this. Ozunu, a man known for the power of his spells, was exiled to the island of Izu on a slanderous charge, an accusation that twisted the truth to bring him down.

The central practice of Shugendō is the peak entry (mineiri, entering the peaks; nyūbu shugyō), pressing deep into the sacred mountains. It is also called sanrin tosō, austerity in the mountain forests.

Tosō means to shake off the dust of the defilements. It corresponds, originally, to zuda (Sanskrit dhūta), the Buddhist discipline of casting off attachment to clothing, food, and shelter. The very act of pressing into the mountains and walking on with sleep and food cut to the minimum becomes, in itself, a practice of shaking the dust from the mind.

At the core of the peak entry lies the idea of ritual death and rebirth (gishi saisei). One lets the everyday self die for a time, is held and purified within the mountain as a womb, and is born anew. On the Dewa Sanzan, the three mountains of Dewa, a funeral is held before the entry that treats the practitioner as one already dead, and the mountains are walked as a "journey of rebirth" that circles Mount Haguro, Mount Gassan, and Mount Yudono. The tainai-kuguri, passing through a rock cave shaped like a womb, likewise derives from this death and rebirth.

In the mountains, the ten realms (jikkai), the ten states of existence from the hells up to buddhahood, are cultivated within one's own body, each likened to a particular practice. This is called the practice of the ten realms (jikkai shugyō). The best known is the "Western Peering" (Nishi no nozoki) on Mount Ōmine: held by a lifeline, the practitioner flings the upper body out over a sheer cliff and chants "Sange, sange; rokkon shōjō" (Repentance, repentance; may the six senses be purified), a practice of casting away the body. The Ōmine Okugake-michi, crossing the ridges from Yoshino to Kumano, is registered as a World Heritage Site and is the most severe course of all Shugendō.

It was on that same Ōmine that En no Gyōja is said to have realized Zaō Gongen. With no origin in India, this is a divinity born in Japan (a gongen, a provisional manifestation). In a wrathful aspect, one leg raised high, flames at his back, he displays the power to crush delusion. He is the deity who stands as the very emblem of Shugendō.

Which realm is likened to which practice in the practice of the ten realms is transmitted differently from school to school and from age to age. This article presents only a general outline.

The yamabushi's white robes and the implements they carry are each said to bear an esoteric Buddhist symbolism. To put them on is, in itself, to take the teaching upon one's own body.

The tokin worn on the forehead is said to represent the jeweled crown of Mahāvairocana. The oi carried on the back is likened to the mother's womb that holds the practitioner within the peaks; the kongōzue staff in the hand is the very Dharma body of Mahāvairocana, and to hold the staff is to contemplate, "I am none other than Mahāvairocana." The iratoka rosary at the waist is likened to the sword of wisdom that shatters the defilements; the yuigesa draped from the shoulders is a sign that the ten realms are possessed within one's body. And the sound of the conch is likened to the preaching of Śākyamuni Buddha.

What the yamabushi wears in the mountains is not ornament. With every step taken, every note blown, these are implements by which the teaching is confirmed through the body itself.

The reading of these symbols differs in detail between the Honzan-ha and the Tōzan-ha and from one age to another. The story that the tokin was bestowed upon En no Gyōja by the emperor is likewise transmitted as a later temple legend. The same kongōzue staff, moreover, is revered on the Shikoku pilgrimage as Kōbō Daishi himself, the honored staff of the dōgyō ninin, the two who walk together as one. In a single implement, the prayers of each path are layered one upon another.

Many, hearing of Shugendō, will picture flames leaping high in the open air. This is the saitō goma.

It is a great homa performed by building an altar outdoors and stacking brushwood and faggots, praying for peace under heaven and an abundant harvest. In the Shingon line, it is said to have been first performed by Shōbō (Rigen Daishi), founder of Daigoji. Its principal deity is Acala (Fudō Myōō). One does not "burn" the homa but "performs" it, and one speaks not of lighting an ordinary fire but of "kindling" the fire of wisdom. For this is no fire of the non-Buddhist paths, but the wisdom-fire (chika) that burns away the defilements.

The wisdom-fire of Acala burns away the fundamental delusion (mumyō, primal ignorance) of all beings. The practice of becoming one with this fire is called kashō zanmai, the samādhi of arising fire. The scriptures teach that for the practitioner to contemplate himself as Acala and abide within the wheel of fire is what is named kashō zanmai. The fire-crossing (hiwatari), walking barefoot over the hot ash of a burnt-out fire, is also transmitted in Shugendō as a practice likened to this kashō zanmai, becoming one with Acala to burn away the defilements.

Here we turn to the "gen" of shugen itself. Some difficult terms will come up, but the core of it is a single thing.

Gen is the practice surely bearing fruit. In the vocabulary of esoteric Buddhism, it is siddhi (shitsuji; the Sanskrit siddhi, that is, accomplishment). It is that very efficacy we mean when we say something is reigen aratakana, "of manifest miraculous power." What matters is this: it is not an inborn supernatural power, but an accomplishment that arises from practice carried out nyohō, according to the correct rite.

In Sanskrit, the practice that brings accomplishment is called sādhana, and the accomplishment that the practice bears is called siddhi. Practice and accomplishment are, from the first, an inseparable pair. The "shu" (to cultivate) and the "gen" (the fruit) of shugen, though different in etymology, closely resemble just this relation of practice and its fruit. Gen does not lie somewhere apart from practice. That it appears of itself when correct practice has ripened is what the Mahāvairocana Sutra teaches, likening the way mantra brings forth siddhi to something as sure as a face reflected in a mirror.

Kōbō Daishi (Kūkai) sets out this siddhi in two tiers. One is the efficacy the practitioner manifests in this world (the siddhi of mantra-holding, jimyō shitsuji): the working that heals illness and wards off calamity. The other is becoming a buddha in this very body (the siddhi of the Dharma Buddha, hōbutsu shitsuji). And the ultimate of gen is this sokushin jōbutsu, Buddhahood in this very body. When the practice of the Three Mysteries (sanmitsu), forming the mudrā with the hands, chanting the mantra with the mouth, and laying the mind upon the Buddha, resonates with the Buddha's working, gen is born, so the teaching runs.

Shugen is often imagined as a path that wins some wondrous power at the end of practice. As we saw in the previous chapter, gen is the fruit of practice; the efficacy of being reigen aratakana, "of manifest power," may well exist. Yet Shugen has never sought that gen as a supernatural power to be obtained and flaunted before others. The warning against showing off reaches back before esoteric Buddhism, to the age of Śākyamuni himself.

The supreme example of the "wondrous power" people imagine in gen is the supernatural marvel (jinpen, a superhuman feat). The scriptures do contain stories of its display. Yet Śākyamuni deeply abhorred displaying such marvels before others. Why? Even when a marvel is shown, a doubter waves it away: "He merely does it by some charm." And so the marvel cannot become a sure sign that awakens faith in others. The same teaching survives, side by side, in the Pāli canon and in its Chinese translation, the Kengo-kyō (Sutra of Kevaṭṭa) of the Dīrgha Āgama.

What Śākyamuni honored most was not the marvel, but the working of the teaching itself, which surely changes the human heart for the good (the wonder of instruction, kyōkai shidō). This warning does not stop with the sutras. In the discipline it becomes an express prohibition; in the treatises it is set in order as reasoned argument; and in time it is carried over, just as it is, into the rites of esoteric Buddhism. We will now trace the sutras, the discipline, the treatises, and the esoteric sources in turn. Each, from its own angle, teaches the same single thing. Not the display of power, but the fruit of practice.

The sutras, the discipline, the treatises, and the rites of esoteric Buddhism alike, from their differing angles, all warn against one and the same thing at the core. What is reproved is not efficacy itself, but the mind that craves it and parades it before others to boast. Gen is what appears of itself when one has rightly accumulated practice and it has ripened. And it is not the power of the practitioner alone, but the result of kaji, the resonance of the Buddha's power with the practitioner's mind, working together in mutual response; so the tradition teaches. And so gen is not something to flaunt, to compete over, or to covet; it becomes a working that helps others when they ask for help. What Shugen held most dear was not the gaining of wondrous power, but becoming a buddha in this very body: sokushin jōbutsu. This warning, reaching back to Śākyamuni, recurs in its own form from the sutras, the discipline, and the treatises through to esoteric Buddhism. Shugen, too, has cherished that same core.

Shugendō took shape when mountain practice joined with the siddhi of esoteric Buddhism. We trace its path of twelve hundred years.

In the Heian period, esoteric monks renowned for the efficacy of their kaji prayer rites were called genza, and at request they went up to the court to undertake the healing of illness and the subduing of malevolent spirits. This was gen not for boasting of power, but for answering people's sickness and calamity. The Pillow Book and the Konjaku monogatari portray genza praying until the sweat ran. Upon this lineage of the genza there appeared people who tempered the power of gen through practice in the mountains, and through the medieval period the distinct path of Shugendō took shape.

Shugendō in time divided into two great streams. The Tōzan-ha, grounded in Shingon esotericism and based at Sanbōin of Daigoji; and the Honzan-ha, of the Tendai line, based at Shōgoin. Though their lineages of teaching diverged, they shared one thing: both placed the core of gen in the siddhi and kaji of esoteric Buddhism.

In 1872 (Meiji 5), by decree of the Grand Council of State, the Shugen school was abolished, and the Tōzan-ha practitioners were ordered to enter the Shingon school, the Honzan-ha the Tendai school. Their lineages are carried on today by the Daigo branch of Shingon Buddhism, the Honzan Shugen school, and others. Changing the form of its Dharma as it goes, the path of gen continues across more than a thousand years.

• The Acala Homa on the 28th of Every Month (Explanation and Application)
• Who Is Acala (Fudō Myōō)? (The Mainstay of the Genza and the Shugendō Practitioners)

Shugendō is a path of practice that makes the mountain itself its training ground. One presses into the sacred peaks, walks on with sleep and food cut to the minimum, performs the fire of Acala, and flings the body out over sheer cliffs. Within such practice of the peak entry, the everyday self dies for a time, is purified, and is born anew.

The fruit that appears of itself when the practice of cultivation has ripened is called gen. It is no inborn supernatural power. It is an accomplishment born of practice carried out according to the correct rite, and at its ultimate stands sokushin jōbutsu, becoming a buddha in this very body.

And so gen was never something to display before others and boast of. The practitioner who has died to the mountain and been born anew turns that very body toward the work of saving others. To enter the mountain and remake oneself, and to give that self over to others. Such is the path that Shugendō is.

Even without entering the mountains, this path is quietly joined to the prayer of joining one's palms each day, of visiting the temple, of remembering those who have passed.