In his novella, Heart of Darkness, author Joseph Conrad uses the theme of fear in order to convey the horror brought to the Congo at the time.
Imagery- Simply looking at the forest brought fear based on the description.
"I saw him extend his short flipper of an arm for a gesture that took in the forest, the creek, the mud, the river seemed to beckon with a dishonoring flourish before the sun lit face of the land a treacherous appeal to the lurking death, to the hidden evil, to the profound darkness of its heart."
Allusion- This quote is a direct allusion to fear and the tone/mood of the story.
There was no joy in the brilliance of the sunshine.
Metaphor- the "thing" that is monstrous is the native running along side the boat.
"We are accustomed to look upon the shackled form of a conquered monster, but there- there you could look at a thing monstrous and free."
Allusion- "...his black death mask..." is alluding to the fact this man in human, and at the time people couldn't see that, see who he really was because of race, like a mask covering his face. And just looking at him brought fear.
"...frown gave to his black death mask an inconceivably somber, brooding, and menacing expression."
Allusion- This quote alludes to the 25 year old man, but the description fits the theme of fear.
"...and no more idea of what would happen to him than a baby. He had been wandering about that river for nearly two years alone, cut off from everybody and everything."