Vishnu decided to be born as Aditi and Kashyap’s son. The son was a dwarf. This was the Vamana avatara (dwarf incarnation) of Vishnu dashavatara which was taken to save Indra’s kingdom.
There was a king of the daityas named Bali. He was powerful and invincible. He was also righteous and truthful. The gods cold not bear to see Bali’s prosperity and began to plot how Bali might be foiled. So well did Bali rule that disease, drought and evil disappeared throughout the three worlds. Bali was the grandson of Prahlada, the son of Hiranyakshyap.
Bali had organised a horse sacrifice. Many sages came to the sacrifice and Shukracharya was the chief priest. The dwarf (Vamana) also arrived at yajna.
Shukracharya, the guru of Daityas, realised that the dwarf was none other than Vishnu. He warned Bali not to promise anything to the Vamana (The Dwarf), who was an incarnation of Lord Vishnu ( a dashavatara).
Bali replied that it would be his honour to serve Lord Vishnu. Bali went to the dwarf and asked what he had wanted. Vishnu expressed the wish that he might be given as much of land as might be covered in three of the dwarf’s steps. This boon Bali readily granted. But no sooner than the boon had been granted, the dwarf adopted a gigantic form.
In two steps, the Dwarf covered the whole kingdom of Bali, from heaven to earth to netherworld and demanded where he should place his third step. Bali offered himself.
Vishnu was charmed at Bali’s generosity.He then appointed Bali king of the underworld and Indra’s kingdom was returned back to him.
Vamana avatar is instantly recognizable with the short frame having a wooden umbrella.
Pictures of Lord Vishnu in various avatars (Dashavatar)
Vishnu took the form of a big fish. There is a story about this in Hindu scriptures. The Asuras or the demons snatched the Vedas, the holy books of the Hindus, and went deep inside the sea. At this point, Vishnu changed his form. He became a matsya, that is, a fish. He entered the sea and brought back the Vedas. There is another story of recreation of human kind after the pralaya, where the sage Manu put all the vedas and other important things in a boat and Vishnu took that to safety.
Here Vishnu took the form of a Turtle (kurma) and then goes the story of the samudra manthan or the churning of the ocean. He provided the base which helped in churning of the ocean. There is another story that when Demons got hold of Amrit, Vishnu helped the gods again in form of Mohini. One Demon had drank some Amrit, Whom Vishnu has cut into two. Thus Rahu and Ketu have been born.