Origin story
Hiranyakashipu won a boon that made him almost invincible: he could not be killed by god or man, inside or outside, by day or night. When he tormented his own son Prahlada for worshipping Vishnu, the lord burst from a pillar as Narasimha, the man-lion, at twilight on a threshold, and killed the demon with his claws.
Narasimha is the fourth avatar of Vishnu and the protector of devotees who hold on to their faith under pressure. His temples in Kerala and Andhra Pradesh, especially those of the Lakshmi Narasimha tradition, invoke the fierce and protective side of the lord.
Source: Wikipedia: Narasimha — https://en.wikipedia.org/wiki/Narasimha
