Dainichinyorai (mahaavairocana in Sanskrit) is a venerable entity of the pantheistic Nyorai (the Dharmakaya Buddha), which is thought of as a unit of the universe itself in Mikkyo (Esoteric Buddhism). Because its light shines over all the world, it is called Hensho or Dainichi.
The symbol of Sanmayagyo is a pagoda in Vajradhatumandala and Gorinto, the five-ring pagoda in Garbha-mandala. Shushi (Mikkyo) (Shuji) was vaM in Vajradhatumandala and aaH or a in Garbha-mandala.
It is a hierarchy of Daibirushanabutsu-Jimpenkaji-kyo Sutra (Dainichi-kyo Sutra) and is the master of Garbha-mandala (the central Eight-Petal Court, or Chuudaiihachiyouin), as described by the Dainichi-kyo sutra. Moreover, it's the center of Vajradhatumandala Gochi-nyorai (Five Wisdom nyorai, or Tathagatas), which the Kongocho-kyo sutra describes. In the Shingon sect, which was founded by Kukai, it is the most important Buddha with which a disciplinant should ultimately integrate. Fudo Myoo is regarded as an incarnation of Dainichinyorai, a fundamental Buddha in Mikkyo or an expression of its inner determination.
In Tibetan Buddhism, which greatly incorporates the latter part of Mikkyo, Dainichinyorai is revered as the center of the Five Buddhas (gobutsu) as well as Gochi-nyorai. In Tibetan Buddhism it is commonly expressed as Nyorai's figure without jewelry or is sometimes drawn as a Buddha having many faces.
The form of statue is expressed by the seated figure like Bosatsu (Bodhisattva), who wears luxurious accessories such as a crown and a yoraku, a string of beads or lace-work used to decorate Buddhist statues and objects. This imitates the figure of ancient Indian royalty. Generally, Nyorai is expressed as a lightly dressed figure free of any accessory, but Dainichinyorai is particularly expressed as a monarch that wears the existence of the universe like an accessory.
The symbolic gesture with the fingers of Vajradhatu Dainichinyorai is Chiken-in (the knowledge-fist mudra), and that of Garbhadhatu Dainichinyorai is Hokkai Join (the Dharma-realm meditation mudra).
About the theory that Dainichinyorai originates from Ahura Mazda
There is a theory that Dainichinyorai (Makabirushanabutsu (Mahavairocana), mahaavairocana) originates from Ahura Mazda, the supreme god in Zoroastrianism. It is based on the attribution of the sun and wisdom and the belief of fire, but there is a large disparity in dharmas between Zoroastrianism and Mikkyo.
There is another theory that Ahura Mazda originates from Varuna, a god of contract in Mitanni and Hittite. This theory assumes that Varuna was a pair of Mithra (a god of light) since ancient times and that he was Asura, but there is no other significant similarity.
Additionally, there is the theory that Dainichinyorai originates from Virocana, the king of the Asura family in Indian mythology. Moreover, the other theory considers it to be a unit of Dainichinyorai that developed from Vairocana, since the name is similar to Virocana, the hierarchy of the Kegon-kyo sutra. It seems that the theory is based on the story of Chandogya Upanishad.
However, in 'the Mahdbharata,' an epic poem of India, Virocana means the sun god but doesn't necessarily mean only King Asura. Moreover, since Visnu as the sun god also has this synonym, it isn't considered to be the immediate origin.
This theory that Dainichinyorai originates from King Asura and the supreme god of Zoroastrianism remains inconclusive.
(In fact, the origins of the other gods are often invalid except for the similarities among names.)
Vajradhatu: On Bazara Dado Ban
Garbhadhatu: On Abira Un Ken
The statue of Yokokura-ji Temple in Ibigawa-cho, Gifu (Kamakura period)
The statue of the To-ji Lecture Hall in Kyoto. The present statue was revived during the Muromachi period.
The statue of Enjo-ji Temple in Nara (late Heian period), made by Unkei
A national treasure
The statue in Toshodai-ji Temple, Nara (early Heian period)
The statue of Kongobu-ji Temple in Wakayama (early Heian period); principal image of Buddha in the former west tower.