King Suratha exclaims that the Devi mahatmya, as recounted by the sage Sumedha, has been wonderful, and now he wishes to know more. What happened after Raktabija was killed by the goddess, what did Shumbha and Nishumbha do. The brahman continued his account.
Nishumbha marched with another army, surrounded by asuras on all sides, as did Shumbha. As expected, a terrible battle was again fought between the two asuras and Chandika. After Nishumbha had struck her lion with a sharp sword, she used a sharp-edged arrow to cut down his sword. A spear hurled by Nishumbha was split in two by her chakra, a trident shattered to pieces with her fist! The daitya finally advanced towards her with a battleaxe, but was brought down by Chandika.
It was now the turn of Shumbha, who proceeded in his chariot, weapons in each of his eight arms. Ambika readied herself with a twang of her bow and by blowing her conch. After a long battle, Shumbha was struck by Chandika's trident, and he too fell down, senseless.
Nishumbha, in the meantime, had regained consciousness, enveloped Kali with ten-thousand chakras from his ten-thousand arms. She cut all of them down and soon pierced his heart with a trident. But another man emerged from within. An unperturned Chandika cut off his head with her sword. With Nishumbha killed, her lion devoured asuras, and Koumari, Shivaduti, Maheshvari, Brahmani, Varahi, Vaishnavi, Aindri, and Kali all killed a great number of asuras on the battlefield.
Reference: Markandeya Purana, translated by Bibek Debroy. Published by Penguin, 2019. The Devi Mahatmya is covered in chapters 78-90 of the Markandeya Purana.