There used to be a rakshasa name Daruka. His wife was named Daruki. They lived in a forest on the banks of the western sea. Parvati had granted Daruki the boon that wherever Daruki went, the forest would follow.
Using this forest as a base, Daruka and Daruki began to oppress the world. They destroyed the yajnas and killed all the righteous people. In desperation, the survivors went to a powerful sage named Ourva. They told Ourva that he alone could save the world from the depredations of these rakshasas. Ourva cursed the rakshasas that if they committed any violence on earth, they would immediately die.
As soon as the gods got to know about this curse, they attacked the rakshasas. The demons were in a fix. If they did not fight with the gods, they would be slaughtered. But if they fought with the gods, they would die because of Ourva’s curse. They decided that they would go and live in the ocean. Thanks to the boon that Daruki had received from Parvati, the entire forest was also submerged in the ocean and became the home of the rakshasas.
There the rakshasa lived. They did not return to earth. But they imprisoned and killed any people who travelled in boats across the ocean.
In this fashion, they once captured a vaishya (the third of the four classes) who was devoted to Shiva. The vaishya set up a linga in the prison and began to pray to Shiva. When the rakshasas saw this, they attacked him with weapons so as to kill him. This vaishya was named Supriya. Shiva gave Supriya a pashupata, a divine weapon associated with Shiva. With this the vaishya killed many demons. The remaining rakshasas were saved by Parvati’s intervention.
The linga that Supriya worshipped is Nagesha.
OM NAMO NARAYANAYA