How does Isaac Asimov use imagery in Nightfall?

Imagery:

". . . the souls of men departed from them, and their abandoned bodies became even as beasts; yea, even as brutes of the wild; so that through the blackened streets of the cities of Lagash they prowled with wild cries."

"He was going mad, and knew it, and somewhere deep inside a bit of sanity was screaming, struggling to fight off the hopeless flood of black terror . . . The bright walls of the Universe were shattered and their awful black fragments were falling down to crush and squeeze and obliterate him."