Mbh 12.281.2a

"'Bhishma said, "In days of yore, Indra, accompanied by the celestial forces, proceeded on his car, and beheld the Asura Vritra stationed before him like a mountain. He was full five hundred Yojanas in height, O chastiser of foes, and three hundred Yojanas in circumference. Beholding that form of Vritra, which was incapable of being vanquished by the three worlds united together, the celestial became penetrated with fear and full of anxiety. Indeed, suddenly seeing that gigantic form of his antagonist, O king, Indra was struck with palsy in the lower extremities. Then, on the eve of that great battle between the deities and the Asuras, there arose loud shouts from both sides, and drums and other musical instruments began to beat and blow. Beholding Sakra stationed before him, O thou of Kuru's race, Vritra felt neither awe nor fear, nor was he disposed to muster all his energies for the fight.[1389] Then the encounter commenced, inspiring the three worlds with terror, between Indra, the chief of the deities, and Vritra of high soul. The entire welkin was enveloped by the combats of both sides with swords and axes and lances and darts and spears and heavy clubs and rocks of diverse sizes and bows of loud twang and diverse kinds of celestial weapons and fires and burning brands. All the celestials with Grandsire at their head, and all the highly-blessed Rishis, came to witness the battle, on their foremost of cars; and the Siddhas also, O bull of Bharata's race, and the Gandharvas, with the Apsaras, on their own beautiful and foremost of cars, came there (for the same purpose). Then Vritra, that foremost of virtuous persons, quickly overwhelmed the welkin and the chief of the deities with a thick shower of rocks. The celestials, at this, filled with rage, dispelled with their showers of arrows that thick downpour of rocks showered by Vritra in battle.