When the battle ensued between the Devatas and the Daityas, the Devatas led by Indra had the upper hand. Daityas went to their Guru, Sukracharya and sought his help. He left for severe Tapas (penance) to please Lord Siva and get the MritaSanjivini Mantra Siddhi. During his absence, the Daityas sought refuge in Usana, the mother of Sukracharya. She assured them protection and she came out of her cottage and using her powers froze the devatas.

Once they became immobile, they became easy targets for the daityas and were subjected to various tortures by the Daityas. The Devatas prayed to Lord Sri Vishnu to protect them and get them out of the predicament. Lord Sri Vishnu understood that the curse on devatas could not be annulled unless Usana was killed. But Usana being a lady was not to be killed as per dharma.

However, Vishnu realised that unless she tried to harm Him, He could not kill her without violating the dharma (No first strike principle!). Vishnu disguised Himself as a ferocious beast and tried to scare Uasana. Usana saw through the disguise of Vishnu and said to Him:

"Vishnu, I am doing my duty of protecting my children and You are supposed to be impartial and protect dharma. You have now become biased and this Adharma cannot be left unpunished. I am going to curse you. You and Indra will be reduced to ash!"

Before these words were spelt out, Vishnu killed Bhrigu's wife with a sharp arrow and separated her head from the torso. Once Usana was killed, her powers also left and Devatas became free. Sage Bhrigu cursed Vishnu to take birth on earth and go through the cycles of birth and death and thus suffer like Us. He brought his wife back to life with his powers. Vishnu accepted the curse of the sage as He accepted the curse of Sage Durvasa. Vishnu stood in an invisible form between the sage and Ambareesha, Vishnu's staunch devotee and took the curse on Himself when the sage was cursing Ambareesha.