In the time of the Satya Yuga, there was an Asura named Vṛtra. Vṛtra and his associates, the Kālakeyas, were at war with the Devas and causing them to suffer greatly. Indra became deeply dejected. Vishnu aided Indra by lending him his power, to which the other gods responded by lending a portion of their own power. The Ṛṣis followed suit by imparting their energy as well, providing Indra with enough power to vanquish Vṛtra. With the aid of his mighty vajra, Indra managed to slay the Asura king.