(details from my drawing "Kali-Raktabija story")
Kālī is the Hindu goddess associated with eternal energy. The name Kali comes from kāla, which means black, time, death, lord of death, Shiva. Kali means "the black one". Since Shiva is called Kāla - the eternal time, Kālī, his consort, also means "the Time" or "Death" (as in time has come). Hence, Kali is considered the goddess of time and change. Although sometimes presented as dark and violent, her earliest incarnation as a figure of annihilation still has some influence. Various Shakta Hindu cosmologies, as well as Shakta Tantric beliefs, worship her as the ultimate reality or Brahman. She is also revered as Bhavatarini (literally "redeemer of the universe"). Comparatively recent devotional movements largely conceive Kali as a benevolent mother goddess.
Kali is represented as the consort of Lord Shiva, on whose body she is often seen standing. She is associated with many other Hindu goddesses like Durga, Bhadrakali, Sati, Rudrani, Parvati and Chamunda. She is the foremost among the Dasa Mahavidyas, ten fierce Tantric goddesses.
The Defeat of Raktabija -
So it was told:
"Skanda, guardian of the heavens, had destroyed many demons who opposed the reign of the gods. But he could not defeat the demon Raktabija. Whenever this demon’s blood touched the ground, a thousand new demons sprang to life. He seemed unconquerable.
"To aid her son in his endeavor to rid the three worlds of the multiplying demon, Raktabija, Parvati (the ultimate Divine Shakti and consort of Shiva) entered the cosmic battlefield as the dreaded goddess Kali – dark as death, gaunt with sunken eyes, gaping mouth, with long disheveled hair covering her naked body. Kali spread her tongue over the battlefield and licked the demon’s falling blood catching on her long, outstretched tongue before the drop could find it’s way to the ground springing a demonic life anew. Raktabija, without his multiplying numbers was left powerless. Skanda was able to dispatch Raktabija and all his remaining duplicates with ease.
"Skanda thanked his mother for her timely help. To celebrate her victory, Kali danced wildly on the battlefield, bedecking herself with a garland of served heads and a girdle of severed limbs.
"Intoxicated with Raktabija’s blood, Kali ran amuck across the three worlds, destroying everything and everyone in her sight. To restrain her, Shiva took the form of a corpse and blocked her path. As the goddess, blinded by bloodlust, tripped on his lifeless body, she was jolted out of her frenzy. She wondered if she had killed her own husband. She placed a foot on Shiva’s chest and brought him back to life. Shiva then took the form of a little child and began to cry, stirring maternal love in the heart of Kali. This forced her to shed her fierce form; Kali became Gauri, the radiant mother, bestower of life, golden."