Nag Panchami

Nāga Panchamī
A Naga being worshiped on Nag Panchami

Nāg Panchamī (Devanagari: नाग पंचमी) is a festival during which religious Hindus in some parts of India worship either images of or live Nāgas (cobras) on the fifth day after Amavasya of the month of Shraavana. Traditionally, married young women visit their premarital households to celebrate the festival. Especially in villages in India, a traditional aspect of the celebration involves joyous swinging by young women on swings temporarily hung on tree branches.
According to Puranic mythology, Brahma’s son Kashyapa had four wives. The “first” wife gave birth to Devas; the second, to Garudas; the third --named Kadroo--, to Nāgas; and the fourth, to Daityas. Nāgas were the rulers of Pātāl-Loka.
The following Sanskrit names of Eight Great Nāgas, namely, Ananta, Vāsuki, Padmanābha, Kambala, Shankhapāla, Dhārtarāshtra, Takshaka, and Kaliya:

अनन्तं वासुकिं शेषं पद्मनाभं च कम्बलम् |
शंखपालं धार्तराष्ट्रं तक्षकं कालियं तथा ||

Transliteration: Anantam Vāsukim Shesham Padmanābham cha Kambalam; Shankhapālam Dhārtarāshtram Takshakam Kāliyam tathā
According to mythology, Lord Krishna had conquered Naga Kālia and put an end to his evil deeds on Nāga Panchamī. According to one mythology, the Kathmandu valley used to be a vast lake. When human beings started to drain the lake to make space for settlements, Nagas became enraged. To protect themselves against the wrath of Nagas, people gave the latter certain areas as pilgrimage destinations, restoring thus harmony in nature.
According to another mythology, a king used his Tantric powers to force Nagas to return to the land rains which they had taken away. The Nagas gave in to the king’s Tantric power, but in recognition of their power to control rains, the king established Naga Panchami festival.
During the festival, Nepalese traditionally post pictures of Nagas above the doors of their homes to ward off evil spirits, offer prayers to Nagas, and place food items such as milk and honey in their fields for Nagas. A few men wearing demon masks dance in the streets as a part of a ritual. Hindus in Nepal have their own myths and legends surrounding Nagas, which lead them to celebrate Nāga Panchamī on a large scale.