Goddess Bhadrakali is one of the fierce forms of the Goddess Durga and there are mentions about her in the Devi Mahatmyam. Worshiped as one of the ten Mahavidyas, Bhadrakali is known for ensuring the victory of the good over evil, as is denoted by the word "Bhadra" itself, which means good.
This Goddess is depicted as having three eyes, four, twelve or eighteen hands and flames flowing from her head. This is a furious form of the Goddess Durga, also worshiped as a Tantric Goddess.
According to one famous story, there was a demon named Darika. He sat to do deep meditation and penance in an isolated forest. He meditated to please Lord Brahma. When Lord Brahma was finally pleased by his penance, he appeared before this demon who had been waiting for him since long.
Lord Brahma asked him the reasons behind such a penance. The demon requested him to make him invincible and grant the wish that he will not be killed by any human being ever. Lord Brahma fulfilled the wish that he would not be killed by any human being ever on this earth.
The demon was pleased and went away laughing. He believed that he had become invincible. As is the nature of a demon, he became overconfident and highly trapped in pride. When finally happy, he started killing all forms of life on the earth. His atrocities found no end.
When Lord Shiva came to know about this wicked demon who had acquired the boon from Lord Brahma, he grew ferocious. He was so highly enraged that he opened his third eye. Lord Shiva opens his third eye only at times of high rage or destruction. From this furious face of Lord Shiva, appeared the Goddess Bhadrakali.
Many a times, various female Goddesses have originated from Lord Shiva when the demons have attacked the earth. All these forms of the Goddesses are known as Maya. Maya is known to trap a being in its various forms as per the need. She traps the demons in pride, under which they commit a mistake, and are lead to death.
So, this furious form of the Goddess Shakti who had emerged from Shiva's face set to fight with the demon Darika. Lord Shiva ordered her to go after the demon and destroy him. When the Goddess appeared before the demon, he laughed aloud, believing that how could a woman kill him. The Goddess took a form too big in appearance, she looked ferocious and had countless hands. The Goddess, accompanied by her other assistants, started a battle with the demon and succeeded in killing him.
It is since then that this form of Goddess Shakti or Goddess Durga is worshiped as Bhadrakali.
The day - Bhadrakali Jayanti - was the day when the Goddess appeared to kill the demon. It is celebrated with huge religious fervor among the devotees of Goddess Durga and among the followers of Shaktism. This day falls every year on the eleventh day during Krishna Paksh in the month of Jyeshtha. This year, Bhadrakali Jayanti will be celebrated on 11th May, 2018, Friday.
Goddess Bhadrakali is worshiped all across the country though with different names.
Many famous temples denoted to Goddess Bhadrakali are Koddungallor, Attukal, Chettikulangra, Thirumandham Kunnu and Chhottanikkara, located in Kerala.