Chapter 3 of the Devi Mahatmya describes the Goddess fighting Mahishasura as he changes between buffalo, lion, human and elephant forms.
Mahishasuramardini
Mahishasura fights the Goddess as he changes between buffalo, lion, human and elephant forms. She confronts him in each form.
Finally, she pins his neck beneath her foot and strikes him with her trident. As he emerges halfway from his buffalo mouth, she beheads him with her sword. She is remembered as Mahishasuramardini, the slayer of Mahishasura.