SatyYuga
Matsya
When the world was at the verge of extinction, he saved Manu (last surviving man and progenitor of the world) by tying the boat containing male and female of each species and the Vedas (sons of Brahma), to its horn and swam to an island in Himalayas where procreation began and mankind Satyusa later, the element 0f purification.
Kurma
Associated with the myth of churning of the ocean (Samudra Manthan) the serpent Vasuki offered himself as a rope, and Mount Mandara was torn out
for use as the churning stick.
As a steady support to hold the mountain I offered to come to earth in the form of Kurma and the churning was successful
Varaha
Hiranyaksha stole the earth (goddess Bhudevi) and dragged her to the bottom of the sea and Lord Vishnu descended as Varaha. The Varaha slew the demon and raised the earth after 1000-year fight, out of the water with its tusks. In some versions Varaha married the earth goddess and she is often shown clinging to one of its tusks with joy and a shy expression Churning of the for stability a fruits of medition.
Narsimha
Hiranyakashipu obtained a boon from Lord Brahma that he can could not be killed by human, animal, inside, outside, day, night, and that no weapon could harm him. Thus, he started terrorizing humanity. He denied the omnipresent Lord Vishnu proclaiming himself god. But his son Prahlad was a devotee of Vishnu and one day in frustration, he challenged Prahlad’s belief “if your god is everywhere, is he in this pillar also?” Thus, from the pillar emerged Narasimha, who tore down Hiranyakashipu with his claws, at dusk, on his lap at the threshold.
