Once there was an asura (demon) who was a great dancer. He was also a great devotee of Lord Shiva and used to appease Shiva through his dancing and devotion. The asura wanted to get Lord Shiva’s blessings and be able to rule over the earth. With this intention on his mind, the asura started to meditate on Lord Shiva. After many years, Lord Shiva was pleased and appeared before the asura. Lord Shiva asked the asura what boon he would like to have. The asura thought for a while and said that he wanted to make anyone he touches on the centre of the head turn into ash (vibhuti). Lord Shiva granted the asura his boon. As soon as the asura got the power from the boon, he said that he wanted to test his powers on Lord Shiva itself. Lord Shiva was stunned for a while and then ran from there. The asura pursued Lord Shiva.
Lord Shiva ran ahead and went to Lord Vishnu for help. Lord Vishnu took the form of ‘Mohini’ , a beautiful damsel, and went towards the asura. The asura was mesmerized by the beauty of Mohini and got distracted from his aim of pursuing Lord Shiva. The asura told Mohini that he wanted to marry her. Mohini replied that she would agree to marry him if he would defeat her in a dance contest. The asura readily agreed and they started dancing. During the contest, Mohini cunningly made a pose in which her hand was touching the centre of her head. Being lost in the urge to marry Mohini, the asura also imitated the same pose and ended up as ash due to his own power. Thus Lord Shiva escaped from bearing the consequence of his own boon.