Within the opening five paragraphs of Edgar Allan Poe's short story "The Pit and the Pendulum," there are a couple of different things that the narrator dreads: The first is the death sentence; the second is total darkness.
The narrator, after having suffered a great deal during the Spanish Inquisition, barely has full control of his faculties in the opening paragraph when his death sentence is given. He is even fading in and out of consciousness, as we see when he says, "The sentence--the dread sentence of death--was the last of distinct accentuation which reached [his] ears." He then proceeds to describe in many details just how horrifying it was to observe the judges pronounce the death sentence; he was only able to observe it because his ability to truly hear anything had already left him due to his state of terror. Prior to the sentence, he had seen the "seven tall candles" standing before the judges as rescuing angels. Yet, as the sentence was pronounced, he grew nauseous, "felt every fibre in [his] frame thrill," and then saw the candles as ghosts, "meaningless spectres, with heads of flame," that would not help him. Then to his horror, the candles were extinguished, leaving him in total darkness in which he again lost consciousness but regained it only well enough to sense himself being carried downwards, for a very long time, to what appears to be a dungeon.
When he gained consciousness in the dungeon, he began dreading opening his eyes because he was too afraid of not being able to see anything at all. As he explains, "It was not that I feared to look upon things horrible, but that I grew aghast lest there should be nothing to see." When he finally does open his eyes, his worst dreaded fear is confirmed, as we see in the following lines:
The blackness of eternal night encompassed me. I struggled for breath. The intensity of the darkness seemed to oppress and stifle me. The atmosphere was intolerably close.
Hence, as we can see, the two greatest things he dreads within the first five paragraphs are the death sentence and total darkness.