Her story
Kali's first major appearance is in the Devi Mahatmya, a Sanskrit text of about the sixth century. In the battle against the demons she springs from the brow of the goddess Durga, a personification of her rage. She cuts down the demons Chanda and Munda, which earns her the name Chamunda, and defeats Raktabija, a demon who multiplied from every drop of his blood that touched the ground, by drinking his blood before it could fall.
A popular telling, the one behind most Bengali images, continues the story: victorious, she could not stop dancing, the earth began to shake, and Shiva lay down in her path; when she stepped on her husband she bit her tongue in shame and stood still. That is the tongue in every image.