How does Bernard Cornwell use imagery in Enemy of God: A Novel of Arthur?

Example of Imagery:

With the Cauldron, he claimed, he could control the Gods and destroy the Christians, and that was why, with a bitter tasting mouth and a belly rank with sourness, I was kneeling on a wet hilltop in Powys.

We came to a fork in the road and there we found our first sign of Diwrnach. It was a skeleton, bound together with horsehair ropes and hung from a pole so that its dry bones rattled in the brisk west wind. Three crows had been nailed to the post below the human bones and Nimue sniffed their stiffened bodies to decide what kind of magic had been imbued into their deaths. 'Piss! Piss!' Merlin managed to say from his litter. 'Quick, girl! Piss!' He coughed horribly, then turned his head to spit the sputum towards the ditch. 'I won't die,' he said to himself, 'I will not die!' He lay back as Nimue squatted by the pole. 'He knows we're here,' Merlin warned me.