In the early Vedic religion, Vritra (Vṛtra वृत्र "the enveloper"), is an Asura and also a serpent or dragon, the personification of drought and enemy of Indra. Vritra was also known in the Vedas as Ahi ("snake"). He appears as a dragon blocking the course of the Rivers and is heroically slain by Indra.
Read more about Vritra: Vedic Version, Puranic & Later Versions