"Anything approaching the change that came over his features I have never seen before, and hope never to see again. He cried in a whisper at some image, at some vision—he cried out twice, a cry that was no more than a breath: "‘The horror! The horror!"
The narrative comes to an end, when we find Marlowe and Kurtz moving back to England, meaning returning to the "civilization" from Africa. Kurtz is not stable mentally and physically, while he is also slowly falling to death on his boat. There he realizes he is near death, utters this phrase as his last words which carry deep meanings. In fact, he refers to all things witnessed and done throughout his stay in Congo. It tells us the experiences, and brutality of Europeans that Marlowe has seen through his eyes. It also sums the experiences and deep-rooted evils in the hearts of civilized people.  Their hostility makes them blind to their surroundings. In addition, the ultimate downfall of Kurtz was due to his own evil actions during his years spent in Congo for the European Company.
Marlow seems to think that it was a profound thing to say, that "he had summed up" and "he had judged" - but summed up what? Judged what? It seemed vague and merely sounded like the crazy last ramblings of a dying man and I felt that either I was missing something or it was deliberately vague. The ‘horror' that Kurtz is speaking of is connected to some kind of truth, as Marlow thinks: "[He] had the appalling face of a glimpsed truth—the strange commingling of desire and hate" (65). I decided that, for a ‘truth' to inspire a "commingling of desire and hate," it must be a profound truth, one that causes the holder of that knowledge satisfaction in possessing that truth. It also must be a disagreeable truth to inspire the ‘hate' that Marlow speaks about.
Perhaps the ‘truth' is connected to the title of the novella: Heart of Darkness. The lack of an article ("a" or "the") in suggests its universality, that all people are capable of immense evil: "All the hearts that beat in the darkness" (65). Whatever this truth may be, the next question is, at what costs is this truth attained? Marlow says that "[Kurtz's summation/judgment was] an affirmation, a moral victory paid for by innumerable defeats, by abominable terror, by abominable satisfactions" (65). For Kurtz, it was death. "But it was a victory!" insists Marlow (65). As for Marlow himself, the cost of glimpsing the heart of darkness is that he will never be a part of civilized society, not completely at least. Africa, Kurtz, the natives and the imperialists' greed have all left an indelible mark on his mind and soul. Indeed, Kurtz is a symbol of this immortality for long past his death, although Marlow has tried "to surrender personally all that remained of him with me to that oblivion," he is ultimately unsuccessful (67). The memory of "him on the stretcher, opening his mouth voraciously, as if to devour all the earth with all its mankind" returns again, along with "the beat of the drum, regular and muffled like the beating of a heart—the heart of a conquering darkness"

During his time spent in Africa, Kurtz becomes corrupt and writes the words "Exterminate all the brutes!" Here he refers to his own and his comrade's brutality in Africa which was carried out in the name of progress and civilization. He induced native Africans to worship and adore him, set up rituals worthy of a brute or a tyrant. As marlow says regarding kurltz, "His was an impenetrable darkness. I looked at him as you peer down at a man who is lying at the bottom of a precipice where the sun never shines". Therefore, by the end Kurtz reflects on his life, which is basically flashing before his eyes in the last moment and let the readers think about the meanings of "the horror.

later in Heart of Darkness I believe that Conrad tells us what the real horror is-life. "Droll thing life is-that mysterious arrangement of merciless logic for a futile purpose. The most you can hope from it is some