Kali is part of the Circle of Goddesses Candle Shrine.  Circle of Goddesses

Kali is a ferocious form of the Divine Mother, who sent her to free the gods from the dominion of the demonic forces. Kali is the goddess of time and of the transformation brought about by the death (Kala) of the ego and of the human personality. Kali represents the spiritual transformation that eliminates the attachments to mundane life and removes the avidya (ignorance) that makes us fear death.

This fearsome Goddess purges us of fear, anger and jelousy. Invoking Kali is a path to destroying evil - both in the outside world and within ourselves. The legend goes that long ago the demons, 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, and sought protection from Mahamaya Durga. Kali, born from Durga's forehead, was 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 has been 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.