Part of the larger Markandeya Purana (4th century CE?), in this Sanskrit text the Devi is extolled as the all-powerful protector of the universe. Also known as Chandi.
The Devas said: ‘O Devi, you who remove the sufferings of those who take refuge in thee, be gracious! Be gracious, O Mother of the whole world; Be gracious, O Mother of the universe; Protect the universe! You are, O Devi, the ruler of all that is movable and immovable!’ (11:2-3)
The standard English translation and commentary is by Thomas B.Coburn: Encountering the Goddess: a translation of the Devi-Mahatmya and a study of its intepretation (Albany, NY: State University of New York Press, 1991). See also Coburn's chapters: ‘Devi: the great Goddess’, in Devi: Goddesses of India, edited by John Stratton Hawley and Donna M.Wulff (Berkeley: University of California Press, 1996), pp31-48; ‘The threefold vision of the Devi mahatmya’ in Devi: the great Goddess, edited by Vidya Dehejia (Washington, DC: Smithsonian Institution, 1999), pp37-57. Also Coburn’s earlier Devi-Mahatmya: the crystallization of the Goddess tradition (Delhi: Motilal Banarsidass, 1984). Another English translation: The Devi-Mahatmyam or Sri Durga-Saptasati (700 mantras on Sri Durga) by Swami Jagadisvarananda (Madras: Sri Ramakrihna Math, 4th ed., 1972).
A French translation: Celebration de la Grande Deesse (Devi Mahatmya) par Jean Varennif (Paris: Societe D’Editions “Les Belles Lettres”, 1975).
This text is also known as Sri Candi, for which see Rajikishore Mishra, ‘A peep into the Candi text’ Orissa Review October 2004, pp34-36  which includes a brief discussion of the Devi Mahatmya in other puranas.