In the beginning of the universe Lord Rudra worshipped Adi-parashakti for Creation. It is believed that goddess Adi- Parashakti had no Form. The Supreme Goddess of Power, Adi-parashakti, appeared in the form of siddhidatri from the Left half Of lord shiva. Goddess Siddhidatri is worshipped on the ninth day of Navratri.
It is believed that Goddess Siddhudatri Provides Direction and energy to planet Ketu. Hence Planet Ketu is governed by her. Goddess Siddhidatri Sits on kamal and rides on the lion. She is depicted with Four hands. She has gada in the one right hand, chakra in the other right hand, lotus flower in the one left hand and shankh in the other left hand.She is the Goddess who possesses and bestows all type of siddhis to her devotees. Even lord shiva got all siddhis by grace of goddess siddhidatri.she is worshipped by not only humans but also by Deva, Gandharva, Asura, Yaksha and Siddha. Lord Shiva got the title of Ardhanarishwar when goddess siddhidatri appeared From his left half.