How does John Gardner use imagery in Grendel?

Example of Imagery:

Though you murder the world, turn plains to stone, transmogrify life into I and it, strong searching roots will crack your cave and rain will cleanse it: The world will burn green, sperm, build again. My promise. Time is the mind, the hand that makes (fingers on harpstrings, hero-swords, the acts, the eyes of queens). By that I kill you.