This story is found in the Brahmandapurana and runs as f0llows:-
In the Kali age there was a Chola King. One day, he went out for hunt and wandered about killing many animals near the Seshachala. Halting at a place for a little rest, he found a handsome young woman plucking flowers. Struck by her beauty, he approached her and asked her for her antecedents. He was told that she was the dughter of a Naga, named Dhanamjaya, who lived in Patala. The
king then conveyed to her his sincere love and asked for her hand. The Naga maid asked the king to obtain her father’s permission but the king did not have the patience to go through the formal process. Ultimately, they married in the Gandharva way and spent the night together happily. Next morning the Naga girl went back to her place. On hearing of her matrimony, her father was pleased. Very soon, she conceived and delivered a beautiful boy. This child grew up into a fine young man. Once the boy asked the mother to show him his father. The mother told him who his father was and showed him the way to the earth. The boy followed his mothers’s instructions and went to the Chola King. The king forgot his relationship with the Naga woman and was doubting the veracity of the boy’s story. Then a divine voice assured the king that the boy was his own son and advised him to crown the son. Pleased with this assurance, the king built a city on the spot where he met the Naga maid and installed the boy as its king. This ruler came to be known as the Chola- chakravarti.
One day, the keepers of his cows came and told this king that every day, as they passed by an anthill, one of the pots was being broken and its milk spilt over the anthill. That night, the king had a dream. A very handsome person black in colour appeared before him and told him “Oh king, I come from Srinivasa and live with him on Seshadri. He lives on the hill with Sri and Bhu. You come and see him.” The king followed him in the dream to Seshadri and there saw a brilliant vimana. Next day, a Sahara came to the king and told him a strange story thus- “Sire, I live on Seshadri cultivating priyangu roots. I offer some of them to the god and eat the rest. Once, I saw Svetavaraha spoiling the crop. I kept my boy to watch the field and myself went in search of honey. On returning, I found that the boy had eaten without the offering being made to god. I got angry and attempted to kill the boy but a divine voice told me that the god had partaken of the food before the boy and asked me to
fetch you to Seshadri…” The Chakravarti asked his ministers to send behind him the milk of one thousand cows and himself followed the Ssbara When they reached the top of the hill, the Sahara showed an anthill to the king and suggested that it might be dug out. The king was afraid of doing so. He caused the milk sent by his ministers to be poured on the ant-hill. The ant-hill melted and out of it emerged the glorious figure of the Lord, bearing Samkha and Chakra in the upper hands, keeping the lower right in varada and the lower left in Katyavalambita. The king praised the Lord in many ways and requested him to stay where he was and as he was. The Lord agreed and asked Ihe king to worship him daily. During the course of the worship he was talking to the king, as if to a friend.
Onee a Brahman, named Krishnasarma, came to the king accompanied by his wife and a baby, told him that he was on a pilgrimage to Banaras and requested the king to kindly grant an asylum to his wife and child till the time of his return. The King agreed A separate house was assigned to the lady and provisions for six months given to her. She was asked not to stir out of the house. Subsequently, the king forgot about this Brahman lady and her child . In course oftime Krishnasarma returned from the pilgrimage and asked for his wife and child. The king sent a servant to fetch them but the servant came back and told the king in secrecy that the rotten skeletons of the lady and her child were to be found in the house. The king was shocked at this and repented for his foolishness in not taking proper care of them. He told the Brahman, however, that the lady has been to Seshachala to see the Lord and that h can meet her the next day. Having thus satisfied the Brahman, he ran to the hill and sought the protection of the Lord. The god commanded his general, Vishvaksena, to fetch some water from the Asthikuta tank and sprinkle it over the two skeletons. When this was done,the lady and her child assumed their former shape and form and got up as if from sleep. The king restored them to Krishnasarma.
Some time later, a demon, named Simhada, settled down on the hill. He did penance and obtained a boon to the effect that no celestial, semi-celestial or human should be able to kill him. He started harassing the Devas thereafter. The Devas sought the protection of the Lord. He asked them to go to his devotee, the Chakravarti, seek his help and enter his body with their amas and they did so. On hearing of their request, the king came to Seshadri and sought the Lord’s guidance. The Lord gave him his own weapons, the Samkha and the Chakra and asked him to go and fight the demon. The king and his men went to the Papanasana-tirtha, where the demon lived, and challenged him to battle. During the bitter fight that ensued, the king used the Lord’s chakra which severed the head of the demon. The king came back to the Lord and offered his sincere thanks. He then returned the weapons but the Lord told the weapons-” Go and live in tirthas named after you. I want to live for sometime without you. In the Kali age, for some reason, a man will invest me with artificial Samkha and hakra. I will hold them just to please the world.”