The head priest of the asuras was Sukracharya, who alone possessed the secret of Sanjivini, the mantra that brought the dead back to life. Thus, any asura killed in battle would be brought back to life while any deva killed would remain dead. The devas were fighting a losing war and in desperation, they asked Brihaspati, their teacher and head priest, to do something.
Brihaspati sent his son Kacha to Sukracharya. ``Become a pupil of Sukracharya,'' Brihaspati told his son, ``get into his confidences and somehow learn the secret of Sanjivini.''
Kacha went to the capital of the asuras and asked Sukracharya to take him as a pupil. ``I am Kacha, the grandson of Angiras, the son of Brihaspati. I am a Brahmana [Brahmin] and I seek to become your pupil,'' Kacha said to Sukracharya. Since no wise teacher could refuse a worthy pupil, Sukracharya agreed.
When the asuras came to know of this, they suspected that Kacha had one aim and one aim only - to get the secret of Sanjivini. So, one day, as Kacha was looking after Sukracharya's cattle, they caught him and tore him to pieces.
When the cattle returned home without Kacha, Sukracharya's daughter Devayani got worried. She had, over time, become very fond of the handsome young man and quite fancied him. She went weeping to her father and Sukracharya, employing the art of Sanjivini, brought Kacha back to life.
The asuras didn't give up. They caught him again when he was in the forest and killed Kacha. They ground his body into a paste and mixed it up in salt-water. Sanjivini was all-powerful, however, and Sukracharya brought Kacha back to life.
The third time, the asuras got smarter. They killed Kacha, burnt his body and mixed the ashes in wine. They then served the wine to Sukracharya, who unsuspectingly, drank it. Again, when the cattle returned home without Kacha, Devayani went weeping to her father.
Employing the Sanjivini, to find where Kacha was, Sukracharya discovered that Kacha's remains were now in his stomach. Devayani would not accept that there was nothing her father could do.
She refused all food and water and began to waste away. Sukracharya was heart-broken at the sight of his beloved daughter growing frailer by the day. He told his daughter that the only way he could bring Kacha back to life was if he allowed his own innards to be split apart. ``It is either me or Kacha,'' he told his daughter, ``you will have to choose.''
Devayani would not make any such choice, saying that both men were important to her. Sukracharya thought long and hard for a way out of the predicament.
Finally, he said to Kacha whose ashes sat crouched inside his stomach, ``I will teach you the art of Sanjivini and then bring you to life. When you come out into the world, use the Sanjivini on me so that Devayani need not grieve for either of us.''
Kacha agreed. Sukracharya brought him out of his stomach, blowing up his innards in the process. Kacha got out of Sukracharya's body, and using the Sanjivini, brought Sukracharya back to life. Having learnt the secret of Sanjivini, there was no reason for Kacha to stay in the kingdom of the asuras. He sought permission to leave.
Devayani addressed him saying, ``grandson of Angiras, I have looked at you with tender longing all these years. Marry me for I shall bring honor both to you and to your illustrious father Brihaspati.''
Kacha had anticipated this. He had his answer ready. ``You are my master Sukracharya's daughter, and I shall always respect you,'' he told her, ``Yet, since I came out of your father's stomach, I am verily your own brother. It is not fit that we marry.''
Devayani pleaded and prodded. She cooed and cajoled. She said Kacha's logic was utter nonsense but Kacha returned to the abode of the devas with the secret of Sanjivini and nothing else.