Once upon a time there was an Asura called Raktabija. Rakta means blood and bija means seed. He had a special boon from lord Brahma.
Raktabija wanted to conquer the world. So he started torturing the men, sages and all other creatures on earth. He also engaged in battles with the Devas.
In one battle Raktabija fought with Goddess Durga and her army. As the goddess wounded the Asura, a few drops of his blood fell on the ground. As soon as they fell on the ground, a clone of him was born from each of them. This was the boon that he got from lord Brahma.
In a short time the battle field was filled with the clones of Raktabija, making the situation much worse for the Devas. There was panic among them.
This infuriated goddess Durga. At that moment goddess Kali appeared from the forehead of Durga. Kali had a fierce look. She had a dark complexion, red eyes, sharp teeth and a long tongue. A garland of skulls hung from her neck. She wore a belt of dismantled limbs around her waist.
With a terrifying roar Kali devoured all the clones of Raktabija. She sucked his blood using her long tongue so that no drop could fall on the ground. And that was the end of Raktabija.
But Kali did not stop at that. After sucking the blood of Raktabija she became bloodthirsty. She got into a frenzy and started a dance of destruction. All creatures were threatened by her. It seemed that she would not stop before the world comes to an end.
When the Devas came to lord Shiva for help, he thought of an idea. He went to the battle field and lay down on the ground. When the raging goddess Kali accidentally stepped on her husband Shiva, she came to her senses. Her bloody tongue came out of her mouth as she was ashamed of her deed.