Story of Matsya avatar of Vishnu and demon Makara, who stole
the Vedas, is found in the Padma Purana. As per this Purana, demon Makara was the
son of Sage Kashyapa and Diti.
Makara was very powerful and he challenged the Devas and
defeated them. Intoxicated with victory of Devas and his huge power, he forcibly
entered Brahmaloka and took away all the four Vedas from Brahma.
He took the Vedas under the ocean and hid it there.
As Vedas were lost, there was no Dharma on earth. Soon Devas
received no yajna and they become powerless. There was utter chaos on earth.
Adharma made its presence felt in the form of Demons and evil men. They ruled
the earth.
To find a solution, Brahma and Devas went to Kshirasagara,
or milky ocean, and offered prayers to Vishnu.
Vishnu promised to bring back the Vedas and with it Dharma
on earth.
Vishnu then took the form of a fish or matsya and entered
the ocean.
He then annihilated the powerful demon Makara and retrieved the
Vedas.