Kansa loved her sister Devaki very much, but during the farewell time of her marriage he listened to the 'Akashvani' (a voice of god) that Devaki's 8th son would kill him. Due to this prophecy Kansa was frightened and in an immediate reaction, he imprisoned both Devaki and the bridegroom Vasudeva.
When Devaki gave the birth to a child, Kansa came and threw the newborn baby, one by one he killed all the newborns. Now the time had come for incarnation of Shri Krishna.
Shri Vishnu ordered His Yogmaya to transplant Sheshji from the foetus of Devaki to the foetus of Rohini. Ultimately the moment of waiting was over. The auspicious moment of the Shri Krishna's coming had come. To relieve the earth, the Shri was taking birth. The whole cosmos appeared radiant. The Shri took birth from the Devaki's foetus. Vasudevji saw that there was a divine child standing before him. There were Conch, Chakra, Mace and Lotus in his four hands. When Vasudev came to know that the Shri Hari himself had taken birth as his son, he was overjoyed. The prison was filled with Shri Krishna's radiance. They got the intuition that the last child is not an ordinary child, It is the Shri, who promised to the world,' I am born from time to time in order to establish true religion in the world' Vasudev and Devaki bowed to the Shri and started praying. Now they became fearless.
Immediately after the birth of Shri Krishna the walls of the prison gave way. So Vasudeva could take away his rewly born child to save the entire generation, He carried him in a basket and went out. It was raining heavily. The river Yamuna was in great flood and its water was rising. Vasudeva wanted to cross the Yamuna and reach the other bank. He was wading through Yamuna, however, when the floodwaters rose very high, Shri Krishna touched the water with his toe and immediately the flood receded. The water made way for Vasudev and there after Shri Krishna was taken to Gokul to stay there incognito.
The same time Jasoda, wife of Nanda gave birth to a baby. Vasudeva kept his kid at their home and brought the newborn baby of Jasoda. He came back to Mathura and doors of prison closed themselves. When Kansa came to know about the birth, he rushed towards the prison and threw the baby in the sky, but this time he could not kill the baby, she skipped from his hand immediately reaching the sky, she was transformed into a divine goddess. She had eight hands, each having a Bow, a Trident, an Arrow, a Shield, a Sword, a Conch, a Chakra and a Mace respectively. At that time all deities from heaven started praising her. She told Kansa “O foolish! What will you get by killing me? Your enemy, who is going to kill you, is already born somewhere else.' and warned Kansa that his killer was born at Gokul and she disappeared in the sky.