what effect would have to the reader ?

WE certainly see the world around the Congo as Marlow sees it. “The flabby, pretending, weak-eyed devil of a rapacious and pitiless folly” is one of the central images with which Marlow characterizes the behavior of the colonists. He refers back to this image at a number of key points later in the story. It is thus a very important clue as to what Marlow actually thinks is wrong about imperialism—Marlow’s attitudes are usually implied rather than directly stated. Marlow distinguishes this devil from violence, greed, and desire, suggesting that the fundamental evil of imperialism is not that it perpetrates violence against native peoples, nor that it is motivated by greed. The flabby, weak-eyed devil seems to be distinguished above all by being shortsighted and foolish, unaware of what it is doing and ineffective. The effect on todays reader becomes one of sadness and horror at the rampant exploiting and downright slavery the native people must suffer under colonial rule.