The fourth Avatar, Narsimha, was
taken in the Satyuga (last age) to kill a tyrant demon king,
Hiranyakashyap. Lord Brahma had given him the blessings that
no known man or animal born in the natural process could kill him,
that he could not die in the day or in the night, on earth or in
heavens, either by fire, water or by any weapon. It was to
kill such a tyrant and to remove him from the earth that Lord Vishnu
assumed the form of Narasimha which was neither man nor animal came
out of a broken pillar, laid hold of the demon king by its teeth,
put him up on his thighs and tore him up in the middle by his claws.
It was evening time (twilight) - neither day nor night.