Flinch, Nausea, Tormentor

Flinch - a small sudden movement, especially when something surprises you or hurts you
Nausea - a condition of feeling sick and the feeling that you are going to vomit
Tormentor - a person who deliberately causes them physical or mental pain

From the surrounding blur, fog, and rain a rough stone wall jumped out. Gurin flinched away avoiding crashing into a suddenly appeared obstacle: the sudden movement made live coals of pain in his head exploded into a firework of blinding lights. The feeling of nausea was unbearable and Gurin bent double supporting himself on the wall that so startled him. He threw up. Damp air drenched with the poignant smell of half-digested food and gastric juice made the man throw up again. He stood there heavily leaning onto the cold, wet stones; his body convulsively shaking, erupting fountains of stenchful greenish liquid; his eyes watering.

Nasty sounds ceased. Not having more strength to cling to the wall, Gurin slipped down into the pool of vomit and rainwater. 

He must go now, whatever the price, he must go. Or it will never end, the endless chase locked up in this forgotten city, a city so forgotten that even sunlight can't find its way there. 

Gurin lifted his head and looked down the alley, or what he thought was the alley. His vision restored now, the man saw with an icy touch of doom to his heart as an unmistakable figure come into sight out of darkness, blurred by streams of rain though with each step becoming clearer and clearer, his eternal tormentor – a man with a pyramid head.