Valakhilyas are a group of divine sages, who are small of body, but great in their ascetic powers. Indeed, according to the Mahabharata, they are only as large as a thumb. Unlike the SaptaRishis, their names are not individually spelt out.
When Kashyapa performed a sacrifice, all deities and sages were asked to contribute.
Indra brought a whole mountain of trees for firewood, but the Valakhilyas were able to bring only a single twig amongst themselves.
Indra made fun of them, and they cursed that his slayer would be born as the son of Kashyapa.
The sages were the size of the thumb but were very powerful due to their piety, Brahmacharya and intense penance. Once, Indra and the Valakilyas were on their way to the ashram of Sage Kashyapa to attend a yajna.
Indra, the king of celestial beings, was haughty and arrogant and this behavior often caused problems to the celestial world. On the way to the ashram, Valakilyas had fallen into water collected in a hoof mark left by a passing animal. Indra, who soon reached the spot, mocked at the tiny sages who were in a puddle and sped away.
Sage Kashyapa received Indra but was a worried man because Valakilyas had not yet reached. Indra then jokingly narrated what had happened and asked Sage Kashyapa to not to wait for the tiny sages.
Sage Kashyapa narrated how powerful the Valakilyas were and he also warned Indra that they might be performing a yajna to replace Indra as the king of Devas.
Soon Indra and Sage Kashyapa reached the spot of the yajna and asked the Valakilyas to desist from it.
The sages relented and said that the one to come from the yajna would Pakshindra, king of all birds, and that bird was Garuda.
With the blessing of Valakilyas, Sage Kashyapa became the father of Garuda.
As Indra made fun of them, they cursed that his slayer would be born as the son of Kashyapa.
However, when Indra apologized and Brahma intervened on his behalf, they modified the curse that the son shall be initially an enemy of Indra, but later will become his friend.
Valakhilya hymns, eleven in number, are the appendix of the eighth Mandala of the Rig Veda. But famous commentators like Sayana rejected them as interpolations. The Ramayana and the Mahabharata have a lot of references to the Valakhilya Rishis.
Valakilyas in Tamil Literature.
Ancient Sangam Tamil literature refers to Valakhilyas in Puranaanuru (verse 43), Tirumurugatrup patai (lines 16-109), post Sangam book Silappadikaram (Vettuvavari 15) and in the poems of middle age poet Arunagirinathar.
The Rig Veda says that they sprang from the hairs of Prajapati Brahma. They are the guards of the Chariot of the Sun. They are also called the Kharwas. The Vishnu Purana describes them as pious, chaste and resplendent as the rays of the sun.
Tamil literature is very clear in saying that the main task of the short and smart ascetics is to prevent human beings from being scorched. So they absorb the excess heat from the sun by travelling in front of him. Tamil books also add they were in turn given energy by Lord Skanda and Goddess Durga.
Even the hunters in the forest pray to Durga for this. Another Tamil poet compares the sacrifice of the Valakhilyas to the sacrifice of the Emperor Sibi who gave his flesh to an eagle to save a pigeon. The famous story of Sibi was referred to in four Sangam Tamil books. Sibi was praised as the forefather of the famous and powerful Tamil Chola dynasty. The food of Valakhilyas is only wind.
Citation and reference.