The Devi Mahatmya sits within the Markandeya Purana and runs to seven hundred verses, which is why it is also called the Durga Saptashati. Its thirteen chapters are grouped into three charitas, each recounting a form in which the Devi meets what threatens the world. It is recited through the nights of Navratri, and its verses are heard at Shakti Peeth shrines across the country.
✦ Did you know
The Durga Saptashati gets its name from arithmetic: sapta-shati, seven hundred verses. It is not a separate book but a section of the Markandeya Purana.
Source: Devi Mahatmya, Markandeya Purana, chapters 81–93