Origin story
In the Devi Mahatmya tradition the Goddess manifests as Bhadrakali to slay the asura Darika, whose boon made him invulnerable to all male beings. Kerala retells the Darika Vadham in Mudiyettu and in temple ritual, and honours the goddess as the protectress of the village.
Her sword, trishula and the severed head of the demon signify the cutting away of ignorance and evil. The lion, the flaming crown and her open palm express fearless power and the assurance of protection, and her kavus remain the ritual heart of many Kerala villages.
Source: Wikipedia: Bhadrakali — https://en.wikipedia.org/wiki/Bhadrakali
Symbolism
Her sword, trishula and the severed head of the demon signify the cutting away of ignorance and evil. The lion, the flaming crown and her open palm express fearless power and assurance of protection.
Mantra
2
Om Bhadrakalyai Namaha
ॐ भद्रकाल्यै नमः
Oṃ Bhadrakālyai Namaḥ
Meaning — Salutations to Bhadrakali, the auspicious and protective Mother.
Recited for: Daily japa, protection, courage
Bhadrakali Bija Mantra
ॐ ऐं ह्रीं श्रीं भद्रकाल्यै नमः
Oṃ Aiṃ Hrīṃ Śrīṃ Bhadrakālyai Namaḥ
Meaning — The three bijas invoke wisdom, energy and abundance, offered to Bhadrakali.
Recited for: Japa for protection from fear and adversity