The myth of Apasmara states that in order to ensure the knowledge in the world is
preserved, he can not be killed. To kill him would mean
attaining knowledge without any dedication or effort, which would
devalue all knowledge and unbalance knowledge and ignorance in the
world. Thus, he is destined for immortality.
Apasmara used to plague humans who prayed to Shiva to control him. According to the myth, because Lord Shiva could not kill Apasmara, he instead took the form of the Lord of the Dance, Sri Nataraja. He performed tandava, the cosmic dance, in order to suppress Apasmara and managed to crush him under his right foot. Thus, because Apasmara must remain immortal, Lord Shiva must remain forever in this form, suppressing Apasmara forever. It is said that Shiva’s stance in doing this is a symbolic reminder of the need to suppress ignorance, ego and laziness in order to realize the truth.