Tripurasura

They were then granted boons by Brahma to have three forts: gold, silver, and iron, which angered the Devas.

[1] The legend of the Tripurasuras is first mentioned in the Taittirīya Samhita of the Krishna Yajurveda: The Asuras had three citadels; the lowest was of iron, then there was one of silver, then one of gold.

They made ready an arrow, Agni as the point, Soma as the socket, Visnu as the shaft.

Rudra let it go; it cleft the Citadels and drove the Asuras away from these worlds.This legend is later told in the Itihāsas and Purānas with more detail.

And if anyone can then destroy Tripura with only a single arrow, that shall be the death destined for us".This rather unusual boon Brahma granted.

The golden fort was built in heaven, the silver one in the sky and the iron one on earth.

They next went to Vishnu, who suggested that if the problem was that the asuras were doing nothing wrong, then the solution was to persuade them to become sinners.

This man's head was shaven, his clothes were faded and he carried a wooden water-pot in his hands.

Since the great sage Narada had been converted, Vidyunmali also accepted the new religion, and in due course, so did Tarakaksha and Kamalaksha.

Shiva called Vishvakarma and asked him to make a suitable chariot, bow and arrow.

When Shiva's army reached the battlefield, the three forts were about to merge into a single Tripura, which condition would last for just a second.

Shiva thus earned Himself the epithet Tripurantaka - the one who ended Tripura, and Paśupatinath - wielder of the Pashupatastra.

Another version that is widely quoted in Tamil literature has Shiva destroying Tripura with a mere smile.

When all the battlefield was filled with warriors, with Brahma and Vishnu in attendance, there occurred the instant when the forts came together.

In Tamil, Shiva has the epithet, "Sirithu Purameritha Peruman" which means, He who burnt the cities with a mere smile.

And once they were at their peak, Vishnu would be reborn as Kalki and wipe them from earth, and once again the world would be free from all kinds of evil and asuras.