City destruction

Angrily she called upon Kṛṣṇa, and departed to Dvārakā; where the people, beholding her, were struck with dismay, and fled for protection to Madhusūdana, the refuge of all worlds. The wielder of the discus knowing that the fiend had been produced by the son of the king of Kāśī, through his adoration of the deity whose emblem is a bull, and being engaged in sportive amusements, and playing at dice, said to the discus, “Kill this fierce creature, whose tresses are of plaited flame.” Accordingly Sudarśana, the discus of Viṣṇu, immediately attacked the fiend, fearfully enwreathed with fire, and wearing tresses of plaited flame. Terrified at the might of Sudarśana, the creation of Maheśvara awaited not his attack, but fled with speed, pursued by him with equal velocity, until she reached Varānāśī, repelled by the superior might of the discus of Viṣṇu.

The army of Kāśī, and the host of the demigods attendant upon Śiva, armed with all kinds of weapons, then sallied out to oppose the discus; but, skilled in the use of arms, he consumed the whole of the forces by his radiance, and then set fire to the city, in which the magic power of Śiva had concealed herself. Thus was Varānāśī burnt, with all its princes and their followers, its inhabitants, elephants, horses, and men, treasures and granaries, houses, palaces, and markets. The whole of a city, that was inaccessible to the gods, was thus wrapped in flames by the discus of Hari, and was totally destroyed. The discus then, with unmitigated wrath, and blazing fiercely, and far from satisfied with the accomplishment of so easy a task, returned to the hand of Viṣṇu.

Vishnu Purana Book 5 Chapter 14