The important point to note here is that a living medium is necessary to invoke the indwelling of a deity. It is through a living medium that Divinity manifests itself. On the sixth day Divinity was invoked in the Bel tree or a branch of it. On the seventh day the Deity is invoked in a group of nine plants known as Navapatrika. The nine plants, which include a branch of Bel tree also, are bundled together, given a ceremonial bath, covered with an orange coloured cloth and installed on a wooden seat on the right side of the image of Durga. This is followed by Mahasnan (great bath) on a mirror, using various materials. After this, consecration and divinization of the image, known as pranapratishtha, takes place. This is followed by elaborate worship of the Devi with sixteen items (shodashopacharapuja). The other deities, attendants and other objects associated with Devi are then worshipped. The Seventh Day's Puja is concluded with bhog (food offering) and Arati to Devi.
As on Saptami, on Ashtami also, Mahasnan and Shodashopacharapuja are done. In addition, nine small pots with flags of different colours attached are installed and the Nine Shaktis are invoked in them and worshipped. After this sixty-four yoginis are worshipped. Then one crore yoginis are worshipped. This is followed by worship of Nava Durga (nine aspects of Durga) and Goddesses Jayanti, Mangala, Kali, Bhadrakali, Kapalani, Durga, Shiva, Kshama, Dhatri, Svaha and Svadha. Ashtami Puja is concluded with Bhog and Arati.
Kumari Puja : Worship of a young girl, treating her as Devi, is also a part of Ashtami Puja. Sri Ramakrishna has said that the Divine Mother manifests herself more in a pure-hearted girl and that is why Kumari Puja is done. He used to bow down before little girls looking upon them as manifestations of the Divine Mother. When Durga Puja was done at Belur Math for the first time, Swami Vivekananda worshipped several Kumaris. Now only one Kumari is worshipped. The same kinds of offerings made to the Devi are given to the Kumari also, and finally Arati is performed. Even senior monks offer flowers at her feet.
Sandhi Puja : The last 24 minutes of Ashtami and the first 24 minutes of Navami (a total of 48 minutes between the two lunar days) constitute the Sandhi or ''Sacred Juncture''. It is considered to be a most auspicious time. At this time Durga is worshipped as Chamunda (that is, Kali who killed the demon Chanda and Munda). This Puja is considered to be the highest point in the whole Durga Puja and the most important ritual.
It is customary to perform bali or animal sacrifice at this sacred juncture. When the first Durga Puja was celebrated at Belur Math in 1901, Swami Vivekananda wanted to have bali done. But Holy Mother prohibited it and, in obedience to Holy Mother's injunction, animal sacrifice is never done at Belur Math. Instead, a banana is 'sacrificed' as a symbolic bali.