As the Devi Mahatmya tells it
Devi Mahatmya, Markandeya Purana 87 and 88 · 3 min read
The demon king Shumbha wanted the Goddess for himself, and when she would not come he sent his generals Chanda and Munda to fetch her, with an army of elephants, horses, chariots and foot soldiers.
They found her sitting on her lion on a golden peak of the mountain, smiling a little.
"Take her," said Chanda, and they came at her with bows drawn and swords out.
Ambika grew angry. As she looked at them, her face turned dark as ink. Her brows drew together, and from the frown on her forehead someone sprang out.
It was Kali. She was gaunt, her flesh dried to the bone, her eyes sunk deep and red. She wore a tiger skin and a garland of human heads, and she carried a sword, a noose and a staff topped with a skull. Her mouth was enormous, and her tongue hung out of it. She roared, and the sound filled every direction.
Then she went into the army.
She picked up elephants in one hand, riders and goads and bells and all, and threw them into her mouth. She did the same with horses, and with chariots, charioteer included, and chewed them. She seized one demon by the hair and another by the neck, trampled one and crushed another against her chest. When they threw weapons at her she caught them in her teeth and ground them up. In a moment the great army was gone.
Chanda came at her with a storm of arrows, and Munda hurled discs by the thousand. They flew at her face and vanished into her mouth like suns going into a cloud. Kali laughed, a terrible laugh, and her teeth flashed. She leapt on Chanda, caught him by the hair and cut off his head. Munda ran at her, and she cut him down too. The rest of the army fled.
Kali picked up the two heads and carried them to Chandika, laughing.
"Here are Chanda and Munda, the two great beasts. I bring them to you for the sacrifice of battle. Shumbha and Nishumbha you will kill yourself."
Chandika spoke to her gently. "Because you have brought me Chanda and Munda, you will be known in the world as Chamunda."
The next demon was harder. His name was Raktabija, blood-seed, and every drop of his blood that touched the ground stood up as another demon exactly like him. The Mothers fought him with thunderbolt and discus, spear and sword and trident, and every wound only made more of him. Soon the whole world was full of Raktabijas, and the gods lost heart.
Chandika turned to Kali.
"Chamunda, open your mouth wide. Catch his blood before it falls, and eat every demon that rises from it. Then he will run dry."
So the Goddess struck him, and Kali drank. Wherever his blood spilled, Chamunda's mouth was there first, and whatever demons sprang from it she ate. At last Raktabija fell, emptied of blood, and the Mothers, drunk on the battle, began to dance.
As Bengal and Odisha tell it: the foot on Shiva
Bengal and Odisha, the night of Kali Puja · 2 min read
Bengal and Odisha go on from where the battle ends. The Devi Mahatmya has the Mothers dancing; here it is Kali who will not stop.
She had drunk too much blood. She danced on the bodies of the slain and the earth shook under her, and she showed no sign of being done. The gods watched her with growing fear. The demons were all dead. If she went on like this, there would be nothing left for her to dance on but the world.
Nobody could get near her. So Shiva went out onto the battlefield and lay down among the dead, flat on his back, directly in her path.
Kali came on, dancing, and her foot came down on his chest.
She looked down and saw whose chest it was. Her husband was lying under her foot.
She stopped. And the gesture she made then is the one every image of her in Bengal still shows: she put her tongue out between her teeth and bit it. In Odisha and Bengal that is what a woman does when she is suddenly ashamed, caught doing something she should not. It is called lajja, and there it is read as plain embarrassment, the shame of a wife who has stepped on her husband. Her fury went out of her in that moment.
Another story, told in Bengal, says where the image came from. The Tantric scholar Krishnananda Agamavagisha dreamed that Kali would show him the form in which she wished to be worshipped, the first thing he saw next morning. At dawn he saw a young woman slapping cakes of cow dung onto a wall to dry. She stood with her right foot forward, and when she noticed him watching, she was embarrassed and put her tongue between her teeth. He knew he had seen the goddess.