Asura · All traditions · Pan-India
Vritra
The dragon of the Rigveda who lies on the mountain and holds back the waters until Indra kills him with the thunderbolt (RV 1.32). Later texts make him a creature of Tvashtri made to avenge his son, a leader of the Danavas, and in the Bhagavata a devotee of Vishnu.
Sources: Hymns of the Rigveda, tr. R. T. H. Griffith (1896), hymns read for the Vedic layer; The Satapatha-Brahmana, tr. Julius Eggeling (Sacred Books of the East 12, 41); The Mahabharata, tr. K. M. Ganguli (1883-96), sections read for the Vedic layer · see Vritra's web