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 (who was not of natural birth) assumed the form of Narasimha. His form was half man-half lion (so he was neither man nor animal). He came out of a broken pillar at the threshold of the palace (neither inside or outside), laid hold of the demon king by its teeth, put him up on his thighs (so he was not killed on earth or in heavens) and tore him up in the middle by his claws (so he was killed not by fire, water or by any weapon). It was evening time (twilight) - neither day nor night.