Narasimha is one of many legendary avatars of the Hindu god Vishnu, one who incarnates in the form of part lion and part man to destroy an evil, end religious persecution and calamity on earth, thereby restoring Dharma.
This depiction of Kali and Shiva references the human experience of death. Kali, who represents dissolution mates with Shiva, who represents creation. She drives him mad and he forgets who he is. For a time, Shiva is lost. Such is death.