Demon Bhasmasura performed intense ‘tapas’ (penance) for several years with only the thought of Lord Shiva. Asur Bhasmasura kept on chanting nothing but Siva, Siva... Finally, Lord Shiva relented and granted the demon the boon that he asked – that he could burn to ashes anyone whose head he placed his hand.
An Asura, Bhasmasura showed his true color and he wanted to test the power of the boon by placing his hand on Shiva’s head.
Shiva fled in terror and sought the help of Lord Vishnu.
Now, Bhasmasura had the evil desire to seduce Goddess Parvati. This was one reason why he was chasing Lord Shiva.
Lord Vishnu who knew about this evil desire took the form of Goddess Parvati. This form of Lord Vishnu is known Lakshmanjati.
Vishnu in the form of Lakshmanjati was able to garner the attention of Bhasmasura. Soon, Bhasmasura forgot about touching Lord Shiva’s head and followed Lord Vishnu, who was in the guise of Goddess Parvati.
Enamored by Goddess Parvati, Bhasmasura lost his mind and became a puppet in the hands of Lakshmanjati. She made Bhasmasura dance by saying that she likes the dance of Lord Shiva.
While dancing she asked Bhasmasura to place his hand on his head and which he did immediately and was reduced to ashes.
This story is found in the Skanda Purana.
(The image on the right is Raja Ravi Varma's famous painting on the Bhasmasura episode.)
There is another version of the Bhasmasura story which suggests that Lord Vishnu took once again the form of Mohini. Vishnu had first appeared in the form of Mohini to trick the demons, and take away Amrut (Ambrosia) during the churning of ocean.
A womanizer, Bhasmasura fell for Mohini’s beauty and she tricked him to placing his hands on his head.
In yet another version, Lord Vishnu appears as himself while Bhasmasura was chasing Shiva and asks what is happening.
When Bhasmasura narrates the entire episode, Lord Vishnu laughs and says ‘only a fool will believe Shiva, who roams the graveyard and wears snakes as garlands.’ ‘If you don’t trust me try placing the hands on your head.’
Bhasmasura was never a true devotee of Lord Shiva. He performed penance and prayed to Shiva with selfish motives - he was only interested in gaining boons, material comforts and controlling the world.
The words of Lord Vishnu created doubts in the mind of Bhasmasura and finally he placed his hand on his head and he was reduced to ashes.