Hyperbole provide a use of exaggeration to make a more impactful effect on it's readers. The quote itself means that the specter is unbelievably frightening to this person. In a bit more depth, stating that "the specter's voice disturbed the the very marrow of his bones" refers to how blood cells are produced. Without blood cells, you're body can't distribute oxygen, stating that this frightening creature was in complete control of him.
