Vishnu as Narsimha was not man or animal, god or demon. He killed Hiranyakashyap with his claws, not by any weapon made under the sun. The demon king died on the threshold of his palace, which was neither outside nor inside. He died at dusk, which was neither day nor night. Brahma's promise remained unbroken, and the world was freed of a cruel and arrogant tyrant.
Order was restored to the world. Indra regained his throne and became once again the ruler of heaven. Prahlad became king of the Daityas in his father's place. He ruled for many years, and was a just and kind king. All through his long life he remained constant in his worship of Vishnu. Prahlad did not die to be born again like other mortals - instead Vishnu took him into himself, and Prahlad became one with Vishnu.
In India, the festival of Holi celebrates Prahlad's triumph over Hiranyakashyap and Holika. Prayers are said to Vishnu, and huge bonfires are lit in the evening, to symbolise the end of the evil Holika.
The Story of Holi