Sharad Navratri begins on the Shukla Pratipada of Ashvin and runs nine nights, each dedicated to one form of Durga: Shailaputri, Brahmacharini, Chandraghanta, Kushmanda, Skandamata, Katyayani, Kalaratri, Mahagauri and Siddhidatri. The nine are not nine goddesses but one, seen at nine depths — beginning with the mountain's daughter and ending with the giver of perfection.

The festival opens with ghatasthapana, the installation of the kalash, performed in the first third of the Pratipada tithi. Barley is sown in earth around the pot and left to sprout through the nine days; the height of the shoots is read as a sign of the year ahead.

Ashtami and Navami carry the kanya pujan, where young girls are worshipped as living forms of the goddess, fed, and given gifts before they leave.

Navratri remembers the nine nights in which Durga fought the buffalo-demon Mahishasura, who could not be killed by any god or man and was slain by the Goddess on the tenth day — Vijayadashami. Across the nine nights she is worshipped as the Navadurga, nine forms from Shailaputri to Siddhidatri, each a stage of her power. In the eastern telling, Rama himself worshipped Durga out of season (the Akaal Bodhan) before crossing to Lanka, which is why the autumn Navratri and Durga Puja fall together.

Sharad Navratri sits at the junction of the seasons (ritu-sandhi), as the monsoon gives way to autumn — one of the two turning points of the year when the body is most vulnerable to change. The traditional nine-day sattvic fast, light and grain-free, is a seasonal cleanse at exactly the moment immunity dips. Barley sown at Ghatasthapana and grown through the nine days is a living reading of the harvest to come.

The nine nights are an inward ascent. Mahishasura is the ego that no ordinary effort can defeat; only Shakti, the awakened feminine power, cuts it down. The Navadurga trace a path from Shailaputri, rooted in the earth, to Siddhidatri, who bestows perfection — the fast and the vigil are meant to carry the observer some way along it, so that Dashami is not only the Goddess's victory but the seeker's.

The asura Mahishasura had a boon that no man and no god could kill him; he had not thought to guard against a woman. He took the heavens, and the gods, unable to fight him, poured their energies together. From that combined light Durga arose, and each god gave her his weapon — Shiva's trident, Vishnu's discus, Indra's thunderbolt — and Himavan gave her a lion.

They fought for nine nights. Mahishasura changed his shape again and again, becoming buffalo, lion, man, elephant, and at the last, as he emerged half-formed from the body of a buffalo, she pinned him with her foot and drove the trident through him. On the tenth day, Vijayadashami, the news of the victory was carried to the world. The nine nights of the battle are Navratri.