Nāga

Nāga is the Sanskrit and Pali word for a deity or class of entity or being taking the form of a very great snake, specifically the king cobra, found in the Indian religions of Hinduism, Buddhism and Jainism. 

Hinduism 

The mythological serpent race that took form as cobras often can be found in Hindu iconography. The nāgas are described as the powerful, splendid, wonderful and proud semidivine race that can assume their physical form either as human, partial human-serpent or the whole serpent. Their domain is in the enchanted underworld, the underground realm filled with gems, gold and other earthly treasures called Naga-loka or Patala-loka. They are also often associated with bodies of waters - including rivers, lakes, seas, and wells - and are guardians of treasure. Their power and venom made them potentially dangerous to humans. However, they often took beneficial protagonist role in Hindu mythology, such as in Samudra manthan mythology, Vasuki, a nāgarāja who abides on Shiva's neck, became the churning rope for churning of the Ocean of Milk. Their eternal mortal enemies are the Garudas, the legendary semidivine birdlike-deity. 

Vishnu is originally portrayed in the form sheltered by a Śeṣanāga or reclining on Śeṣa, but the iconography has been extended to other deities as well. The serpent is a common feature in Ganesha iconography and appears in many forms: around the neck, use as a sacred thread wrapped around the stomach as a belt, held in a hand, coiled at the ankles, or as a throne. Shiva is often shown garlanded with a snake, Maehle states that "Patanjali is thought to be a manifestation of the serpent of eternity". 

Buddhism

The Buddhist nāga generally has the form of a great cobra, usually with a single head but sometimes with many. At least some of the nāgas are capable of using magic powers to transform themselves into a human semblance. In Buddhist painting, the nāga is sometimes portrayed as a human being with a snake or dragon extending over his head. One nāga, in human form, attempted to become a monk; and when telling it that such ordination was impossible, the Buddha told it how to ensure that it would be reborn a human, and so able to become a monk. 

In the "Devadatta" chapter of the Lotus Sutra^[각주:1], the daughter of the dragon king, an eight year old longnü (nāga), after listening to Mañjuśrī preach the Lotus Sutra, transforms into a male Bodhisattva and immediately reaches full enlightenment. This tale appears to reinforce the viewpoint prevalent in Mahayana scriptures that a male body is required for Buddhahood, even if a being is so advanced in realization that they can magically transform their body at will and demonstrate the emptiness of the physical form itself. 

Nagas are believed to both live on Mount Meru, among the other minor deities, and in various parts of the human-inhabited earth. Some of them are water-dwellers, living in streams or the ocean; others are earth-dwellers, living in underground caverns. 

The nāgas are the followers of Virūpākṣa^[각주:2], one of the Four Heavenly Kings who guards the western direction. They act as a guard upon Mount Sumeru, protecting the dēvas^[각주:3] of Trāyastriṃśa^[각주:4] from attack by the asūras^[각주:5]. 

Among the notable nāgas of Buddhist tradition is Mucalinda, Nāgarāja and protector of the Buddha. In the Vinaya Sutra, shortly after his enlightenment, the Buddha is meditating in a forest when a great storm arises, but graciously, King Mucalinda gives shelter to the Buddha from the storm by covering the Buddha's head with his seven snake heads. Then the king takes the form of a young Brahmin and renders the Buddha homage. 

It is noteworthy that the two chief disciples of the Buddha, Sariputta and Moggallāna are both referred to as Mahānāga or "Great Nāga". Some of the most important figures in Buddhist history symbolize nagas in their names such as Dignāga, Nāgāsēna, and, although other etymons are assigned to his name, Nāgāsēna.

In the Vajrayāna and Mahāsiddha traditions, nagas in their half-human form are depicted holding a naga-jewel, kumbhas of amrita, or a terma that had been elementally encoded by adepts. 

According to tradition, Prajñapāramita sutras had been given by the Buddha to a great Naga who guarded them in the sea, and were conferred upon Nāgārjuna later.

1. one of the most popular and influential Mahayana sutras, and the basis on which the Tiantai, Tendai, Cheontae, and Nichiren schools of Buddhism were established. According to Paul Williams, "For many East Asian Buddhists since early times the Lotus Sutra contains the final teaching of the Buddha, complete and sufficient for salvation." [본문으로]
2. one of the Four Heavenly Kings representing the cardinal direction of the west in Buddhist cosmology. [본문으로]
3. A deva in Buddhism is one of many different types of non-human beings who share the godlike characteristics of being more powerful, longer-lived, and, in general, much happier than humans, although the same level of veneration is not paid to them as to buddhas. The concept of devas was adopted in Japan partly because of the similarity to the Shinto's concept of kami. [본문으로]
4. The Trāyastriṃśa heaven is an important world of the devas in Hindu and Buddhist cosmology. The word trāyastriṃśa is an adjective formed form the numeral trayastriṃśat, "33" and can be translated in English as "belonging to the thirty-three [devas]". It is primarily the name of the second in the six heavens of Buddhist cosmology, and secondarily used of the devas who dwell there. [본문으로]
5. An asura in Buddhism is a demigod or titan of the Kāmadhātu. They are described as having three heads with three faces each and either four or six arms. [본문으로]