The Hindu gods attained immortality and invincibility by worshiping a divine Linga called the "Atma-Linga". The Lanka King Ravana wanted to attain immortality by obtaining the Atma-Linga (Soul of Shiva). Since the "Atma-Linga" belonged to Shiva, Ravana worshipped Shiva with devotion. Pleased by his prayers, Shiva appeared before him and asked him what he wanted. Ravana asked for the "Atma-Linga". Shiva agreed to give him the boon on the condition that it should never be placed on the ground before he reaches Lanka. If the "Atma-Linga" was ever placed on the ground, it would be impossible to move it. Having obtained his boon, Ravana started back on his journey to Lanka.