Ashtami Tithi of every month is dedicated to Goddess Durga. The belief comes more from the nine days of Navratri festival where many people observe a grand celebration of the day and celebrate. While the main Ashtami festival falls during Navratri, the Ashtami Tithi of every month is also observed due to the same significance.
There lived a demon named Durgam. He was very wicked and had caused chaos all around. He became a trouble for all the gods. All the three worlds wanted relief from his atrocities. It is said that all the gods went to Kailash and reached out to Lord Shiva for help. This included Lord Vishnu and Lord Brahma as well. All the gods combined their powers together and created the Goddess. After giving her a powerful weapon, they asked the Goddess to destroy the demons.
There are nine main forms of the Goddess, all of which are worshipped during Navratri. Among these, Goddess Mahagauri is worshipped on the eighth day, Ashtami. During Masik Ashtami also, Goddess Mahagauri is worshipped. It is said that the Goddess showers her blessings on the devotees on this day. Goddess Mahagauri is often depicted giving her blessings while her hands are in Varun and Abhaya mudra. The other two hands of four are depicted holding Trishul and Damru. She is shown mounted on an ox and wearing a green saree.
The fast can be observed by both men and women. Without eating anything and by staying just on fruits, the fast can be performed both the ways. It goes unsaid that the devotees should abstain from non-vegetarian food items as well as alcohol, and from people who have consumed these should not be hosted by the devotees at their home. That is why it is said that the worship of Goddess Durga is very difficult.
Devotees offer prayers even to the weapons of the goddess on this day. Hence, the day is also known as Veerashtami. The goddess is offered red flowers, red sandalwood paste and a lamp is lighted before her, and some offerings of foods and fruits are made. She is offered Panchamrit consisting of milk, ghee, curd, honey and sugar. The devotee should, while holding rice grains and flower in his hands, chant the following Mantra:
Sarva Mangala Mangalye Shive Sarvarth Sadhike
Sharanye Triyambake Gauri Narayani Manoustute
The flower and rice grains should then be offered to the Goddess. After this, Durga Chalisa is recited and this is followed by the Arti.