"My child, you need not know much in order to please Me.
Only Love Me dearly.
Speak to me, as you would talk to your mother,
if she had taken you in her arms."
Maa Kali is the fearful and ferocious form of the mother goddess Durga. She assumed the form of a powerful goddess and became popular with the composition of the Devi Mahatmya, a text of the 5th - 6th century AD. Here she is depicted as having born from the brow of Goddess Durga during one of her battles with the evil forces. As the legend goes, in the battle, Kali was so much involved in the killing spree that she got carried away and began destroying everything in sight. To stop her, Lord Shiva threw himself under her feet. Shocked at this sight, Kali stuck out her tongue in astonishment, and put an end to her homicidal rampage. Hence the common image of Kali shows her in her mêlée mood, standing with one foot on Shiva's chest, with her enormous tongue stuck out.
Kali Puja is done to diminish the ego and all negative tendencies that hinder spiritual progress and material prosperity. Performed on the night of Kartik Amavasya, which falls in October/November, Kali Puja is an intense invocation to the fearsome goddess. The main purpose of the puja is to seek the help of the goddess in destroying evil - both in the outside world and within us.
The legend goes that long ago the demons, Shambhu and Nishambhu, disturbed the peace of Indra, the king of gods, and his empire (heaven). After extensive and endless battles, the gods lost all hope and the demons became stronger.
The gods took refuge in the Himalayas, the holy mountains, the home of Lord Shiva and Parvati. The shaken gods sought protection from Mahamaya Durga, the goddess of Shakti. Kali was born from Durga's forehead as Kal Bhoi Nashini, created to save heaven and earth from the growing cruelty of the demons. Along with Dakini and Jogini, her two escorts, she set on her way to end the war and kill the devils.
There was chaos all around. After slaughtering the demons, Kali made a garland of their heads and wore it around her neck. In the bloodbath, she lost control and started killing anyone who came her way. The gods started running for their lives. The only source of protection seemed Lord Shiva, Durga's consort.
Seeing the endless slaughter, Shiva devised a plan to save the world. He lay down in the path of the rampaging Kali. When the goddess unknowingly stepped on him, she regained her senses. The well-known picture of Ma Kali, with her tongue hanging out, actually depicts the moment when she steps on the Lord and repents.
That momentous day is celebrated ever since. Kali, also called Shyama Kali, is the first of the 10 avatars (incarnations) of Durga. Kali Puja is performed essentially to seek protection against drought and war, for general happiness, health, wealth, and peace. It is a tantrik puja and performed only at midnight on Amavasya (new moon night) in November.