There is an interesting story in the Adbhuta Ramayana of Mata Sita taking the form of Goddess Kali to annihilate the thousand-headed Ravana. In the seventeenth chapter of the Adbhuta Ramayana, Mata Sita reveals the existence of a thousand-headed Ravana, the elder brother of the ten-headed demon, describing the information she had received from a Brahmana during her youth.
Upon hearing this revelation, Rama embarks on a mission to
invade the Pushakara Dvipa, the dwelling place of the thousand-headed monster,
with the intent of defeating him. In the ensuing and ferocious battle, Rama
falls unconscious (sections 18 to 22).
Witnessing this dire situation befall Rama and his forces,
Sita undergoes a startling transformation into the formidable form of Goddess Kali,
ultimately annihilating the demon and his entire army. She is assisted in this
endeavor by numerous manifestations (section 23). Rama awakens and is astounded
by the presence of Kali (section 24).
He extols her with an extensive hymn encompassing 1008 names
(section 25). Although it is named "Sita-Sahasranama" (meaning 'a
thousand names of Sita'), the majority of the names pertain to the Shakti cult.
Sita subsequently reverts to her original form after dissolving her Kali
manifestation. Having achieved victory, Rama returns to Ayodhya and resumes his
rule (sections 26 and 27).