Trivikrama

Vamana
Four-armed Vamana
Devanagari	वामन
Sanskrit transliteration	Vāmana
Affiliation	Human dwarf and fifth Avatar of Vishnu
Weapon	Wooden umbrella and water pot

Vamana (Devanagari: वामन, IAST: Vāmana, lit. dwarf) is described in the Puranas as the fifth avatar of Vishnu, and the first incarnation of the Second Age or Treta yuga. He is the first avatar to appear as a human, although he does appear as a dwarf Brahmin.

Aditi took Payovrata to propitiate Lord Vishnu. As a result, Vamana was born to Aditi and Kashyapa. He is the twelfth of the Adityas.

The Bhagavata Purana describes that Vishnu descended as the Vamana avatar to restore the authority of Indra over the heavens, as it had been taken by Mahabali, a benevolent Asura King. Bali was the great grandson of Hiranyakshipu, the grand son of Prahlada and son of Virochana.

Vamana, in the guise of a short Brahmin carrying a wooden umbrella, went to the king to request three paces of land. Mahabali consented, against the warning of his guru, Sukracharya. Vamana then revealed his identity and enlarged to gigantic proportions to stride over the three worlds. He stepped from heaven to earth with the first step, from earth to the netherworld with the second. King Mahabali, unable to fulfill his promise, offered his head for the third.

Vamana then placed his foot and gave the king immortality for his humility. He was also allowed to return every year to see the citizens of his country. The festival of Onam for some and first day of [Diwali] for some is related to this return of Mahabali.

...
Wikipedia