text: Vritra broke Indra's two jaws during the battle, but was then thrown down by Indra and, in falling, crushed the fortresses that had already been shattered. For this feat, Indra became known as "Vṛtrahan" (lit. "Slayer of Vritra" and also as "slayer of the first-born of dragons"). Vritra's mother, Danu, who was also the mother of the danava race of asuras, was then attacked and defeated by Indra with his thunderbolt. In one of the versions of the story, three devas – Varuna, Soma, and Agni – were coaxed by Indra into aiding him in the fight against Vritra, whereas before they had been on the side of Vritra (whom they called "Father").
  Hymn 18 of Mandala IV provides the most elaborate account of the Vedic version. The verses describe the events and circumstances leading up to the battle between Indra and Vritra, the battle itself, and the outcome of the battle.
  Puranas
  As told in the narration given to King Yudhishthira in the Mahabharata, Vritra was an asura created by the artisan god Tvashtri to avenge the killing of his son by Indra, known as Triśiras or Viśvarūpa. Vritra won the battle and swallowed Indra, but the other deities forced him to vomit Indra out. The battle continued and Indra was eventually forced to flee. Vishnu and the rishis (sages) brokered a truce, with Indra swearing that he would not attack Vritra with anything made of metal, wood or stone, nor anything that was dry or wet, or during the day or the night. Indra used the foam (which Vishnu had entered to ensure victory) from the waves of the ocean to kill him at twilight.
  The Srimad Bhagavatam recognizes Vritra as a bhakta (devotee) of Vishnu who was slain only due to his failure to live piously and without aggression. This story runs thus: