Commonly seen between 800 and 1300 AD, the tantric cult of the Yoginis was borne out of worship to sixty-four specific goddesses who promised to bestow shakti, or magical powers, to their most ardent devotees. The Yoginis represented forces of vegetation and fertility, illness and death, Yoga and magic. All Yoginis are worshipped collectively, each one having a specific place in a circular plan similar to the spokes on a wheel. The texts used in this practice are written in a secret language known as sandhya bhasha, or "twilight language," which ensure they cannot be used by the uninitiated without an experienced teacher. The number sixty-four, being a multiple of 8, is considered to have magical powers in the numerology of India, and is also an extension of the eight matrikas that joined Durga in her great battle against Mahishasura; each matrika evolved into eight further goddesses. In rare instances, some cults recognize nine matrikas (The Saptamatrika consisting of Brahmi, Maheshvari, Kaumari, Vaishnavi, Varahi, Indrani and Chamundi, joined by Candika and Mahalakshmi), each generating nine additional goddesses, for a total of eight-one Yoginis.