Once, Agastya Muni was wandering through the forest when he came across a tree where he found several individuals hanging upside down. Intrigued, he asked, "Who are you?" They replied, "We are your forefathers. Because you have no son and have not achieved perfect self-realization, we are suffering in this state. Either you must now have a son who can perform sraddha* for us and release us from this predicament, or we will continue to endure this, waiting for your complete self-realization." (*Sraddha - Offerings of food and drink made to the deceased, accompanied by sacred rituals to nourish, protect, and support their journey from lower to higher realms.)
Determined to rescue his forefathers, Agastya approached a king and requested his daughter's hand in marriage. However, the king replied, "I have no children." Agastya then warned the king about the fate of his forefathers and summoned all the beauty of the universe into one place, which transformed into a baby girl. He presented the girl to the king, saying, "Here is your daughter. Raise her, and she will mature into a young woman in just one week. I will return then to take her as my wife."
As fate would have it, this unfolded as Agastya had foreseen. However, when he brought her to his ashram and proposed that they conceive a child, she expressed, "If you wish to live as a grhastha (Householder) with me, you must provide suitable opulence. I was raised by a king, so the ascetic life does not suit me. Nevertheless, I am your wife, and I will serve you regardless. But if you desire to maintain your current lifestyle, then do not ask me to bear you a son. I will serve you as a brahmacarini*." (*Brahmacarini - a female who pursues sacred religious knowledge.)
Determined to fulfill her desires, Agastya Muni sought charity from a king. The king took him to the treasury and handed him his account book, saying, "Examine the earnings and expenditures. If you find any surplus, it is yours." However, Agastya, upon reviewing the accounts, discovered that the king had no surplus; all his tax collections were spent on the welfare of his people.
Agastya then inquired if there were other kings with great wealth, and the king directed him to another monarch. Agastya suggested that this king accompany them to seek charity as well, given his need for additional funds. Together, they visited this new king, only to find a similar situation: he had no excess wealth. Undeterred, Agastya and the two kings proceeded to yet another king's palace, but the outcome was the same.
Agastya finally asked the fourth king, "Please inform me of anyone who possesses unused wealth." The king revealed, "In the forest dwell two demon brothers named Illvala and Vatapi. They have killed numerous rishis and kings and plundered them by inviting travelers into their abode for a meal. Illvala cooks Vatapi and serves him to the guests, claiming it is goat flesh from a sacred fire yajna. After the guests partake, Illvala calls 'Vatapi, come out!' and Vatapi bursts out of the guest's stomach, killing him. Then these two consume the guest and take his wealth. This gruesome act has made them exceedingly wealthy, and they use their wealth for nefarious purposes."
Agastya, accompanied by the four kings, ventured into the forest and arrived at the dwelling of the two demons. Illvala welcomed them and offered what he claimed was goat meat. However, when he briefly left the room, Agastya advised the kings, "Do not consume anything." Upon Illvala's return, he questioned why the kings had not eaten, to which they replied, "We are observing a fast. Only our guru partakes of food." Illvala then placed all the food before Agastya, who consumed it all. Afterwards, rubbing his belly, Agastya declared, "Vatapi, chiro bhava [Vatapi, be digested]."
Illvala shouted, "Vatapi, come out!" but to no avail. The kings informed him, "This is Agastya Muni, who is aware of your actions, Illvala. He knows that you have murdered many rishis and kings. You must devise a plan to appease him, for he is angry and will soon digest you, just as he has digested your brother."
Agastya, glaring at Illvala with wrathful eyes, announced that he would now face the consequences of his sins. Illvala humbly begged, "I will offer anything to spare my life." Agastya responded, "Then bestow all your wealth upon these kings." Using his mystical powers, Agastya transported all the wealth and the four kings to the Himalayas, to his ashrama. He summoned his wife, and she beheld the entire valley filled with gold.
Agastya then requested charity from the kings, who complied, and his wife agreed to conceive a child. A son was born to them shortly thereafter. Agastya Muni departed from his wife and returned to his life as a renounced sage.