How does Donna Cross use imagery in Pope Joan?

Imagery:

The men released Theodorus, and he fell forward onto his knees. Then he raised his head and Anastasius screamed in terror. The face was dreadful. Blood poured from the black and empty holes where Theodorus's eyes had been, streaming from his chin onto his shoulders and chest. Anastasius buried his face in his father's side. He felt his father's large hands on his shoulders and heard his voice, strong and unwavering. "No," his father said. "You cannot hide, my son." The hands impelled him, pushing him away, turning him back toward the grisly scene before him. "Watch," the voice commanded, "and learn. This is the price exacted for lack of subtlety and art. Theodorus pays now for wearing his loyalty to the Emperor so openly."

She went to the altar. Loosening her cap, she placed a mass of her hair upon the altar. It curled thickly over the smooth stone surface, almost white in the dimming light. She lifted the knife. Slowly, deliberately, she began to cut.