The tithi of navami in the month of Ashwin, during the Ardra nakshatra within Pitru Paksha, marks the start of the first and most powerful kalpa of Durga upasana. In this form, Bhagwati Durga takes the form of the eighteen-armed Ugrachanda, who destroyed the Asura lord during the first of three kalpas in which this battle occurred. While not widespread, this upasana is still practiced in some places in Bengal, the Kamakhya temple and certain Tantrik kulas.
The goddess is invoked in her 18-armed vigraha, a trishula, or a khadga and is worshipped ritualistically with bali as per vidhan for 14 days until Vijayadashami tithi. Ardra nakshatra is linked with strong Tantrik karmakanda. This astadasabhuja form is distinct from the Mahalakshmi of the Durga Saptashati, who also has 18 arms. Ugrachanda’s mantra upasana is rare, and her unique and extremely powerful mala mantra is considered one of the greatest vidyas in existence.
Ugrachanda is mentioned in a group of 8 goddesses known as the Ashtashakti-s of Chandika, who are worshipped during the invocation of Devi Durga. This group includes Ugrachanda, Prachanda, Chandogra, Chandanayika, Chanda, Chandavati, Chandarupa, and Atichandika.
A text (Brihaspati Samhita) mentions the following about these forms with respect to a certain upasana:
“..the Goddess should be invoked and worshipped at the head of a spear, or at a sword-blade, or in a book, picture, or a yantra. The Goddess should be contemplated as respectively holding a human skull, a dagger, a bell, a mirror, a tarjani, a bow, a banner, a small drum, and a noose in her left hands, and a spear, a club, a trident, a thunderbolt, a sword, a mace, an arrow, a discus, and a rod in her right. The different manifestations of the Goddess, such as Ugrachanda, Prachanda, Chandogra, Chandavati, Chandarupa, and Atichandika, should be as well worshipped on the occasion. Of these, Ugrachanda is coloured like yellow pigment. Prachanda is coloured like rosy dawn; Chandogra is dark brown; Chandanayika is blue; Chandarupa, yellow; and Atichandika, grey. Each of these divinities should be contemplated as standing sideways on a lion, with her left leg elevated and thrust out. Mahisasura (half man, half buffalo) should be contemplated as charging the deity, who has got a sword in one hand and has caught hold of the hair of the asura in the other. The Mantra of ten letters (Dashakshari), which is most dear to the Goddess, should be mentally recited by the votary; after which the trident of the Mahadevi must be worshipped.”
