Prahlada, son of the demon Hiranyakashipu who was the Lord's worst enemy, was one of the greatest devotees of Lord Narayana. Wanting to avenge the death of his brother, Hiranyaksha, the demon king performed such severe tapas that even Brahma melted and granted him a boon rendering him all powerful and ruling supreme over the three worlds. The demon king was so arrogant that he had forbidden everyone from even uttering Lord Vishnu's name. It was an irony that his own son, Prahlada, constantly prayed to the Lord and sang his praises.. His teachers Skanda and Amaraka, who were Shukracharya's sons, were surprised at the boy's unshakeable devotion. The king got to know of it and asked one of his servants to take the boy to the forest and kill him. He got him tortured, tied him with the varunapasha and threw him into prison. Gradually, the father was forced to accept defeat. The father and son entered into a duel as a challenge during which Lord Vishnu emerged out of a pillar in Narasimha avatara and killed the king. Vishnu's anger and fury came down only after he saw his devotee, Prahlada's loving countenance. Prahlada begged Him to release his father from all his sins and the Lord readily granted his devotee's wish. In fact, he went further and sent the demon king to heaven. Lord Vishnu blessed Prahlada and said that he would be the emperor of the vast world and be his devotee forever.