Before the Samudra Manthan, the power of the demons lied in a sacred mantra which was called Mrtu Sanjeevani mantra which was recited by the preceptor of the demons Rishi Shukracharya. Because of this powerful mantra, the demons that were killed by the Devas in war again came back to life and attacked the Devas again. As the Devas were unaware of this mantra, they were losing the battle and succumbing to the evil forces.
To overcome this problem the Devas design a plan and they request Rishi Brihaspati’s son Kacha to go and learn the mantra from Shukracharya. For Dharma to prevail, Kacha agrees to put his life at risk, goes to the Rishi and requests him to take him as his disciple to which the Rishi agrees. The demons try to persuade him from taking Kacha as a disciple as he belonged to the enemy clan. But Shukracharya denies their persuasions on the basis that knowledge should not be denied to anybody who asks for it.
In a short time, Kacha becomes the favourite of Rishi Shukracharya with his services and humility. Not only the Rishi, but he becomes the heartthrob of the Rishi’s daughter Devyani too. The demons come to know about this and kill Kacha. Bu on Devyani’s request, Kacha is bought alive by his guru with the help of the mantra. Despite several attempts of the demons, Kacha is bought alive every time with the help of the Sanjivani mantra.
Not to fail in another attempt, the demons kill Kacha, and mix his ashes in Madira and give it to Rishi Shukracharya to drink. Devayani comes to know about it and informs it to her father, but it is too late. This puts the Rishi in a fix if he has to bring Kacha alive, he had to die. But trusting his disciple, Rishi Shukracharya brings Kacha alive in his stomach and teaches him the Sanjeevani mantra. Then he requests Kacha to come out of his stomach and bring him back alive with the same mantra.
Kacha’s purpose to learn the mantra for the Devas was fulfilled with this. He had all the opportunity to work for the advantage of the Devas by not bringing back the Rishi alive. But, as a true disciple he agrees and comes out of the stomach of his Guru and then with the mantra learnt, he brings Shukracharya alive. Although only on a mission to learn the Mantra, Kacha follows Dharma and does his sincere duty towards his Guru.
Pleased by his selflessness, the Rishi offers Devayani’s hand in marriage, but Kacha refuses on the ground that as he was reborn from his Guru’s stomach, he would become a brother in relation to Devayani and hence cannot marry her. On this, Devyani gets upset and curses that the Sanjeevani mantra would be of no use to him. But Kacha abides to it, saying that his purpose was to learn the mantra for Dharma, but not for his own use and comes back and teaches it to the devas thus making them powerful as the demons.
Kacha is a less known personality, yet great for his selfless thoughts. For Dharma, he puts his life at stake and goes to the enemy camp and risks his life. Although the mantra is useless for him, he believes in the greater good and teaches it to the Devas. With his selfless act, he becomes the saviour of Devas and Dharma.