The most chanted mantra and powerful mantra of Maa Durga is this mantra. It is said that this mantra has immense power.
Sarva-Mangala-Maangalye Shive Sarvaatha-Saadhike I
Sharanye Trayambake Gauri Narayani Namostute II
Meaning of Mantra
We bow to you O Devi Narayani. You are the the auspicious for everyone, you bring happiness . You are the one who completes every work for everyone. You are protector of everyone. You are the one with 3 eyes and a beautiful face. We salute you, O Narayani.
She is the most auspicious one and the one who bestows auspiciousness upon all the worlds. She is pure and holy.
Maa protects those who surrender to her and is also called the three eyed one and Gauri (daughter of mountain king). I bow down to Mother Durga who is the sister of Mahavishnu.
Manifestation of Devi Durga
Goddess Durga manifested to kill the demon Mahishasura or the buffalo faced demon. Till then, the demon Mahishasura appeared invincible and was troubling all the worlds beyond compare. The heavens and the worlds suffered heavily in his evil hands. The gods and humans were praying fervently to Brahma, Vishnu and Shiva seeking to put an end to the miseries they suffered in the hands of the demon. Time passed with no hopes. It was then that goddess Durga manifested in response to the prayers of all.
Information on some more mantras is given below:
Yaa Devi Sarva Bhooteshu Vishnu Maayethi Sabdita
Namastasyai Namastasyai Namastasyai Namo Namaha
Meaning: Salutations again and again to the Devi (Goddess) who dwells in all living beings as power and maya of Lord Vishnu.
Mantra for warding off all the evils & mishappenings
Om Jayanti Mangala Kali, Bhadrakali Kapalini Durga Kshama Shiva Dhatri Swaha Swadha Namoastute.
ॐ जयंती मंगला काली भद्रकाली कपालिनी
दुर्गा क्षमा शिवा धात्री स्वाहा स्वधा नमोऽस्तुते
Chanting and understanding the meaning of these Mantras bring fulfillment to human beings.