Raktabīj was a demon and commander of Chand-Mund. He had a boon that whenever a drop of his blood fell on the ground, another Raktabīj would be produced at that place.
Rakta = blood, bīja = seed; "he for whom each drop of blood is a seed"
The eighth chapter of the Devi Mahatmya, raktabIja-vadh (Slaughter)
When Raktabīj was injured, each drop of blood falling to the ground produced other Raktabīj. Goddess #Kali collected blood from the body of the Raktabīj in a khapar (skull bowl)and drank it so that the Raktabīj could not come back alive. This form of Kali who drank the demon's blood is also called Rakeshwari.
Eventually, the Raktabīj became an apocalypse. After killing Raktabeej and his entire army, Goddess Kali's fury did not subside and took a vikral form. To calm Kali, Lord Shiva intervened who placed himself in their path. As soon as Kali stepped on Shiva's body she was in surprise and embarrassed she took out her tongue.