This happened in the Krita Yuga (Golden Age). Hiranyaksha, an asura, dived into the ocean. To rescue earth, Lord Vishnu assumed the form of a wild boar, Varaaha, and went after the asura. Varaaha overpowered Hiranyaksha in the duel that he fought under the water, and restored earth to its original position in the universe.
Varaaha achieved this magnificent feat with apparent ease, and the only sign of his exertion was a drop of sweat, which fell on the ground. A fully grown young warrior arose from this drop of Lord Varaaha’s sweat. His name was Naraka.
Bhoodevi or Mother Earth took a liking to this son of hers and asked Lord Varaaha that her son should become invincible. Varaaha pulled out one of his tusks and gave it to Naraka saying he could use it as a weapon whenever he was in great danger.
“Use your great powers to do only good, son,” said Lord Varaaha. “Uphold dharma.”
Naraka went away to seek his fortune.
“I’ve no doubt he will become the most powerful warrior in the three worlds,” said Bhoodevi expressing admiration for her son.
“Powerful, he will certainly be,” said Lord Varaaha. “Will he also uphold dharma? What makes an individual great is his adherence to dharma.”
Centuries rolled by. Krita Yuga was followed by Treta Yuga and then came Dwapara Yuga (we are in the Kali Yuga that followed the Dwapara Yuga). By then, people who had acquired power but brushed aside dharma had grown in number. Simply put, upholding dharma means being kind, truthful, caring and helpful. Its opposite, adharma, means being untruthful, arrogant, violent and destructive.
Lord Vishnu would take birth on earth to uphold dharma and to root out adharma. Each of his births is called an avatar or the descent of the Lord.
In the Dwapara Yuga, Lord Vishnu had come down to Earth as Krishna, the Yadava hero. He vanquished his wicked uncle Kamsa. He brought about the destruction of kings who were not adhering to dharma.
Meanwhile, Naraka had grown very powerful. Ruling from his impregnable fortress of Prag-jyotisha-pura or the land of the rising sun, he had conquered earth and heaven. Drunk with power, he snatched away the celestial ear rings of Aditi, the mother of the devas.
Indra, the Lord of the devas, sought Krishna’s help to vanquish the invincible Naraka. Sathyabhama, one of Krishna’s wives, was upset when she heard about the misdeeds of Naraka. She urged her husband to act. Armed with his Sudarshana chakra and other weapons, Krishna left for Prag-joyitisha-pura. Sathyabhama went with him. Both of them rode on Garuda, the celestial eagle, which served as a vehicle for Krishna.
To strike at Naraka’s capital, Krishna had to penetrate four layers of its defenses. He flew over the outermost ring of walls made of rocks, he crossed the rings of fire and of spears. Whoever tried to stop him was struck down. The chief defender of Naraka’s fort was Mura. Confident that none could penetrate the rings of defenses he had set up, Mura was relaxing deep down in the ring of water. As each layer of defense crumbled under Krishna’s attack, it caused violent ripples in the water, arousing Mura out of his slumber. Then he heard an ear shattering sound — it was Krishna blowing his conch, Panchajanya.
Enraged, Mura rushed out to stage a counter attack. He fell fighting Krishna, who earned the name, Muraari, the enemy of Mura.
Ultimately Naraka himself came out of his palace to battle Krishna. The two fought day and night. It was hard to say who was more powerful. Naraka was saving the weapon given to him by his father, Lord Varaaha, precisely for such an occasion. On the dark night of Chaturdashi, the fourteenth day of the fortnight of new moon, Naraka took out the deadly tusk of Lord Varaaha and threw it at Krishna. Struck in the chest Krishna fell unconscious. Even as Naraka raised a cry of victory, Sathyabhama picked up the bow and continued the fight. In Satyabhama, Naraka found a worthy foe. He had no clue as to how to stop her onslaught.
As the duel between the two raged on, Krishna opened his eyes. Naraka was startled to see Krishna stand up. If the dreaded weapon of Lord Varaaha had failed, it meant only one thing — his opponent was none other than Lord Varaaha himself, his father. Naraka was dazed. Lord Varaaha’s warning words now rang in his ears: “Use your powers to do only good, son. Uphold dharma.”
He had failed to follow his father’s advice. He meekly submitted, as Krishna threw his Sudarshana chakra at him.
As his life was webbing away, Naraka joined his hands in salutation to Krishna and Sathyabhama. Moved at the sight of the fallen asura, Sathyabhama rushed to him.
Krishna silently watched the reunion of mother and son. Sathyabhama was none other than Bhoodevi, born again!
Naraka saw the light in his dying moments. The darkness was lifted as the dawn broke. That day is celebrated as the festival of lights, Deepavali or Diwali, which signifies that we have to emerge from darkness to light.
(Adapted from the Mahabharata and the Bhagavata Purana.)