Narasimha & Vamana Avatara

This special form was adopted by Lord Vishnu to kill a demoniac ruler Hiranyakashyap, who had pleased the Lord Brahma with his religious offerings. 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 Narasingh 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.

The fourth lineal descendant of Hiranyakashyap, named Bali, through his devotion and penance defeated Indra, the god of firmament, humbled other gods and extended his authority over the three worlds. All the gods appealed to Lord Vishnu for protection and He became manifest in His Dwarf Avatar of Vaman for the purpose of restraining Bali. Once when this king was making a great religious offering, Lord Vishnu in the form of Vaman appeared before him in the company of other brahmins. Bali was extremely pleased to see a holy man with such a diminutive form and promised to give him whatever he should ask. Lord Vishnu asked only for as much land as he could measure by three steps. Bali laughingly agreed to grant the boon of three steps. Lord Vishnu as dwarf stepped over heaven in first stride and earth in the second stride. Then out of respect to Bali's kindness and his grandfather Prahlad's great virtues, Lord Vishnu stopped short and left him in pathal, the subterranean region. Bali's capital was Mahabalipuram.