its body was contorted with agony , surrounded and pressed in from all sides by three distorted creatures of black wrought iron : diseased unicorns the size of clydesdales , emaciated , skeletal at many points , yet with slabs of muscle that bulged in brutal exertion as they crushed the man between their shoulders and chests , muscles that clenched like tree roots on their straining necks as they reached down with black teeth to tear at the screaming face .