Lord Narsimha is the 4th Incarnation (Avatar) of Lord Vishnu and is supposed to be the most fierce avatar as per Ancient Vedic Texts and Scriptures. Lord Vishnu took this avatar to destroy the demon king Hiranyakashyapu who was determined to stop anybody from worshipping any Gods including Lord Vishnu. Demon king Hiranyakashyap has a brother known as Hiranaksh who took the Earth into Paatal Lok. Lord Vishnu took the avatar of Varaha (Boar) and freed Earth from Hiranaksh by killing him.
Demon King Hiranyakashyapu got very agitated due to killing of his brother by Lord Vishnu and to take a revenge, he did a very prolonged Tapasya to please Lord Brahma. Ultimately, Lord Brahma had to appear to give a Boon to Hiranyakashyapu who demanded that he should be blessed with immortality which was declined by Lord Brahma. Thereafter, he sought a blessing that he should not be killed by any Human, Demon or Animal, in the Day or Night, Inside or Outside and by any type of Weapon which was granted to him by Lord Brahma.
Once, armed with the boon granted by Lord Brahma, Demon King Hiranyakashyap declared that he himself is a God and passed a dictat that henceforth everyone in his Kingdom should worship him and anyone not obeying this will be slayed. After this, everyone started offering prayers to Demon King Hiranyakashyap. However, unfortunately his own son Prahlad was a Ardent Devotee of Lord Vishnu and he refused to worship Hiranyakashyapu which agitated the Demon King to the extent that ultimately, he started trying to kill his own Son but all his efforts went to vain since Prahlad was saved everytime by Lord Vishnu.
After all his attempts to kill his own son Prahlad failed, Demon King Hiranyakashyap once again tried to reason with him as a last resort and hence, he called Prahlad to his court room in the evening. However, Prahlad refused to heed to any of his reasonings which angered Hiranyakashyapu to the extent that he drew his sword to kill Prahlad with his own hands. As a last question, he asked Prahlad if it was true that Lord Vishnu being omnipresent according to Prahlad was present in all the Pillars of the court room as well and thereafter, struck the pillar with his sword.
The moment Sword struck the pillar, Lord Narsimha came out of the Pillar roaring as his upper half was the form of a Lion and killed Demon King Hiranyakasyap with the Nails of his bare hands by keeping the Demon King on his lap so that the boon granted by Lord Brahma was honoured as well as the Demon King was slayed.
Thereafter, Lord Narsimha became synonyms with the Fierce form of Goodness for destroying any kind of Evil. Hence, Lord Narsimha is supposed to bless his worshippers for Protection against all kinds of Evil and Negative force, Miseries and Misfortunes, Enemies and other similar harmful forces.
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