We have all heard of the 10 incarnations of Lord Vishnu. But Lord Shiva donned numerous incarnations, which are described in Shiva Purana under the chapter “Shatarudra Samhita.” Let’s look at one story –
As per Bhagavta Purana, Hiranyakashipu was once Jaya, a gatekeeper of Lord Vishnu who was born as a human due to a curse from Kumaras. With severe penance, he pleased Lord Brahma and asked for a boon of invincibility and immortality – He shall neither die at the hands of a man, nor a beast or a devil, he will not die in the day or in the night, nor by steel, stone or wood, neither indoors nor outdoors, neither sky nor earth. With this boon, he believed he became invincible. He became egocentric and dictatorial. He ordered that he must be worshiped as a God in his kingdom and began a ruling filled with terror. His son Prahlad however was a devotee of Lord Vishnu and never complied with his father’s order. And so Hiranyakashipu tried to kill his very own son several times. And when he could not kill him, he tortured him for days and challenged him to prove God’s existence. It was then, Lord Vishnu appeared out of pillar in his Narsimha avatar – His fourth incarnation and killed Hiranyakashipu.
Since Lord Vishnu had put all his destructive powers into this incarnation of His, Narsimha could not control his fury even after killing Hiranyakashipu. He was hell bent on destroying all the three universes. Terrified with this, Gods and demigods called upon Lord Shiva for help.
The gods pleaded, ‘My Lord, the Narsimha avatar will destroy everything in the three universes. Please Lord, save us.’
Comprehending the severity of the situation, Lord Shiva created his avatar, Veerbhadra and sent him to stop Narsimha. Veerbhadra tried to reason with Narsimha but no logic seemed quite sufficient for Narsimha to cease his destructive actions. Veerbhadra then transformed into half lion, half bird –Sharaba avatar and plunged into a war with Narsimha.
The selves of Lord Rudra were imposed in Sharaba. Even the form with he was speeding towards Narsimha looked like the distorted from of Rudra. He had thousands of heads and displayed matted locks in each of them. All his heads were decorated by a silver, crescent moon. Like a vicious bird, it appeared with its nails and beaks and wings. His persona was quite frightening. He used his adamantine claws as his weapons. His arms were huge and were paired with four huge legs. He displayed his black neck and flew straight like a blazing fire.
Sharaba caught hold of Narsimha and took him high in the sky. Then he dropped him to the hard ground with absolute force. The Narsimha figure got split into two and before he died he acknowledged the power of Lord Shiva.
Sharaba then changed into his prior form of Veerabhadra and skinned Narsimha. The devotees believe that this is the skin that Lord Shiva wears and the skull of Narsimha is adorned by him as a necklace.