Puranic tradition, recorded in sources including the Bhagavata Purana and the Vishnu Purana, narrates that the demon king Hiranyakashipu, having obtained near invincibility through austerity, grew furious that his own son Prahlada refused to worship him and remained instead a devoted follower of Vishnu. After numerous failed attempts to kill or dissuade Prahlada, Hiranyakashipu enlisted his sister Holika, who possessed a boon or garment granting her immunity to fire, to carry the boy into a blazing fire while she herself sat unharmed within it.
According to the narrative, Prahlada's unwavering devotion to Vishnu protected him: Holika's protection failed her instead, and she burned to death in the fire while Prahlada emerged completely unharmed, a reversal the tradition presents as evidence that righteous devotion outweighs even a specifically granted supernatural protection when it is misused for evil purpose.
The episode connects directly to the subsequent narrative of Vishnu's appearance as Narasimha, a being neither fully man nor fully animal, who kills Hiranyakashipu at twilight, neither day nor night, on a threshold, neither inside nor outside, using his own claws rather than any weapon, satisfying the precise and narrowly worded terms of the boon that had made Hiranyakashipu believe himself unkillable.