This kavacham comes from the Ganapati Khanda of the Brahmavaivarta Purana. The sage Narada asks Narayana for the ten-syllable mantra of Bhadrakali and her armour; Narayana gives both, and tells their lineage — given by Narayana to Shiva for the battle with Tripura, by Shiva to the sage Durvasa, and by Durvasa to King Suchandra, who with it conquered the whole earth.
The heart of the hymn is a mantra kavacham: instead of only naming forms of the goddess, it places her seed syllables — Om, Hrim, Shrim, Klim, Krim — together with her names over the head, eyes, nose, teeth, lips, throat, ears, shoulders, chest, navel, back, hands and feet. Then eight forms of Kali guard the eight directions, and the mother of the universe guards above, below, on land, in water and in the sky.
The closing verses say that all great gifts, austerities and vows are not worth a sixteenth of this armour — and that without it, even a hundred lakh repetitions of the Kali mantra do not bear fruit.