Ravana therefore decided that he would immolate himself. Ravana, as you know, had ten heads. He lit a fire and severing his heads, began to offer them one by one to the fire. When nine of the heads had thus been offered, Shiva appeared.
Enough is enough, said Shiva. What boon do you want?
Please grant me the boon that I may be very strong. And please restore my nine heads, replied Ravana.
These boons Shiva granted and the place where Ravana prayed is known as Vaidyanatha.
The gods were not at all happy that Ravana had become so strong. They were afraid tha the rakshasa might start to oppress them. They therefore sent Narada to create some mischief. Narada met Ravana and asked him why he was looking so happy. Ravana related the story of the boon.
Boon, exclaimed Narada. Who believes in Shiva? Let me see if you can lift up Mount Kailasa. If you can do that, I shall indeed believe that you have become strong.
Incited by Narada, Ravana returned to Kailasa and lifted up the mountain. As the mountain shook, Shiva and Parvati were disturbed. Shiva cursed Ravana that soon a being would be born who would kill Ravana. This being was of course Rama, Vishnu's incarnation.