How Lord Vishnu appeared in front of Prahlada? The story of appearance of Lord Vishnu for Prahlada is mentioned in Vishnu Purana’s 14th chapter.
As soon as Prahlada began to pray the Lord, his Nagpash broke and the mountains that the demons had thrown into the sea also lightened up causing great relief for Prahlada. Lord Vishnu appeared before him and said- “O Prahlada! I am pleased with your devotion. You may seek any boon of your wish.” Prahlada said- “May I always have an unconditional devotion for you. May your remembrance never be away from my heart.”
God said – ” Your devotion for me shall always remain the same. Now, seek anything you wish.” Prahlada said- “O Lord! My father has always cultivated hostility for you because of my devotion. May my father be free from the sin of his action.” Lord said- “O Prahlada! All your wishes shall come true but still seek any boon of your choice.”
Prahlada said- “O Lord! I don’t want anything other than devotion for you.” Lord said -” O Prahlada! You have nothing in your mind but devotion for me, so with my grace, you will attain supreme abode.”
Saying this, the Lord disappeared. In later course, ultimately Hiranyakashipu decided to kill Prahlada himself. He tied Prahlada to a pillar and shouting abusively for God, he hit the pillar. As soon as he hit the pillar, it broke and Lord appeared from it in Narsimha incarnation. His appearance was extremely formidable with half human and half lion form. Dragging Hiranyakashipu to the threshold, He killed him with his powerful talons. After the killing of his father, Prahlada took over the throne and ruled his subjects religiously.