Ganesha begins the tale of Vishnu's fourth avatar...
When Lord Vishnu in his avatar form of Varaha the boar defeated the Demon Hiran and saved the earth, everyone rejoiced, save one person, Hiran's Brother, Hiranyakashipu or Kashipu, for short. Kashipu was beyond angry over his brother's death and he focused that anger on Vishnu and his followers. He plotted revenge against the god but had to come up with a plan before he would be able to attack Vishnu. In order for this evil demon to kill Lord Vishnu, he would have to act completely out of character.Kashipu would have to be the absolute symbol of all that is good in the world.
Kashipu's goal was to gain powers from the god Brahma that would enable him to defeat Vishnu. For thousands of years, Kashipu lived a life of goodness. He went on many fasts and pilgrimages in the forest. He gave to others even when he had little to spare. He would even worship the gods for many hours every day, including the god Vishnu. Brahma was so impressed by the selfless acts and good deeds of the demon Kashipu, that he promised him a boon as a reward.
Brahma could not take back his offer and granted the boon to Kashipu. Vishnu was incarnated, once again, in order to bring down the evil demon. In this avatar, Vishnu is half-man and half-lion and goes by the name Narasimha. What follows is the tale of the evil demon Kashipu and the heroicism of Narasimha.
Kashipu, although granted one boon, packed a lot of details into the gift from the god Brahma. He knew he would have to be very precise if he wanted to be able to survive any type of attack and be able to eventually kill Vishnu.
"Brahma, I thank you for your generous boon. All I ask for is that I not die from any creature that you have created. May my death not occur inside or outside of any place, during the day or during the night, up in the sky or down on the earth. May my death not come from any weapon, human or animal, including anything living or not. May I not be killed by any demigod, demon, or snake. You have no rival that could destroy you on the battlefield and I wish for the same. I want to rule over all that live and all who are in heaven. Grant me all the mystic powers of the universe!"
"Is that all?" Brahma laughed. "I give, but truly you should be careful for the intentions behind such a boon. Those who have everything will surely lose it all," Brahma warned.
Kashipu ignored Brahma's warning and went on to live the life he felt he was destined to all along. Having nothing to fear and command over everyone, it did not take long for him to start pushing around the world. Kashipu called down Maya and demanded that he build him the most beautiful palace that the world had never seen before. He also circled the world looking for the most beautiful bride he could find. He found his bride, a young beautiful princess named Kaya. Kaya was the most innocent and lovely creature to walk the earth but could not refuse Kashipu no matter how much she would have wanted to. Kaya tried to stay away from her husband as much as possible, which wasn't hard because he was always traveling from the heavens and earth to prove his rule over every being. Soon Kaya became pregnant with a son and feared for the child's life. Before her husband, Kaya had been a follower of Vishnu. She still was but was not allowed to outwardly worship the god because of her husbands disdain for Vishnu.
One day when Kashipu was out pushing around some kings, Indra and other gods came to attack the mansion of Kashipu. Narada took this opportunity to come down and steal away the pregnant Kaya. Kashipu decided that he had millions of wives in both heaven and on earth, so he could live with one less. Narada protected Kaya and when her son, Prahlada, was born, Narada took it upon himself to train the child. Prahlada was raised to worship Vishnu and was in love with the god.
Many years later, Kashipu started to feel a little fatherly and decided to visit his children around the world. His first visit was to his first-born son Prahlada. He was outraged when he learned that his son worshiped his enemy Vishnu. He tried to get his son to stop but Prahlada could not be discouraged. Kashipu then tried multiple times to murder his son but Prada was always protected by Vishnu. Kashipu called down Vishnu to finally settle the fight between the two but something else entirely showed up to fight.
Narasimha, an avatar of Vishnu, was summoned by the lord Brahma to finally destroy Kashipu. In the choice of Narasimha, Brahma had to be very careful so as to not break the boon that he had given to Kashipu. Kashipu had to be destroyed to end his terror over the heavens and earth. Narasimha would finally bring the terror to an end. Narasimha who was part man and part lion, picked Kashipu up with ease, carried him to the entrance of the mansion, put him over his knee, and proceeded to disembowl him. Narasimha was able to kill Kashipu because he had asked protection from god, man, and animal but Narasimha was none of these. Kashipu is not killed at day or night but at twilight in the entrance of his own home which is neither inside or outside. On Narasimha's knee, Kashipu was neither in the air or on the ground but in between. Kashipu had been defeated.
With the death of Kashipu the world could once again rejoice and praise the Lord Vishnu and his avatar Narasimha.
So ends the tale of Vishnu and his four animal avatars.
Narasimha
Source: Wikipedia. Link
Avatara 4-Narasimhavatara(Lord Vishnu in Lion Form)
Web Source: Samasya