In Mahavishnus Dashaavataar, the fourth incarnation is of Lord Narasimha and this is believed to have happened on the holy hill of Ahobilam..
The Asura king Hiranya Kashipu once obtained a boon from Lord Brahma that he should not be killed either by a man or a beast, at day or night, on earth or heaven, or with the help of any weapon. The demon ordered all his subjects to worship only him and not any other God as he felt he possessed all the powers and could not be defeated by anyone. The son of this Asura king was a gifted child by name Prahlada. He had Upadesha (lessons) from Maharishi Narada even when he was in his mothers womb and was born as an ardent devotee of Lord Vishnu. Child Prahlada refused to obey his fathers orders and injunctions. Unable to bear this defiance, the demon continued to put his child to untold miseries. Hiranya Kashipu ordered his men to feed Prahlada poison and throw him from the top of the hill and fling him into the sea.
Being a staunch devotee of Lord Vishnu, Prahlada chanting the name of Narayana surfaced every time they attempted to kill him. A desperate Hiranya Kashipu one day asked Prahlada to show where his God was. Prahlada in all politeness answered: The Lord is everywhere in the pillar and even in a blade of grass.
This provoked Hiranya Kashipu, who in anger targeted a pillar with his mace. To his rude shock, Lord Vishnu emerged from within the pillar in a strange form with a thunderous bolt. It was half man and half lion (known as Nara-Simha Nara means man and Simha is lion), and it was twilight, neither day nor night. The time had come now for Hiranya Kashipu to meet with death. Narasimha dragged the demon king to the threshold of the palace and, keeping him on His lap, tore his chest open with his nails, thus fulfilling all conditions laid down by the Asura himself for his death. Prahlada was crowned the King in the presence of the Devas and Rishis. The hill tribes of this area, known as Chenchus, enjoy a special privilege in the Ahobilam temples. Legends say that when Vishnu took the form of Narasimha, He came down to this hill. His consort Lakshmi, who could not bear the separation, also followed Him to the hill. They fell in love with each other, married and settled on the enchanting hill.