'Between the flashes of lightning the air was dark and terrible', and this gives the image of an almost pitch-black night, only lit intermittently by the 'flickering' lightning. Flickering is a perfect word for this, as the author conveys a mental image of exactly that.
The 'threat of the sky' is the driving force for the savage dance.
Golding's repetitive use of the boys' dialogue 'Kill the beast! Cut his throat! Spill his blood!' adds the sense of both a ritualistic chant and a horrifying murder. Of course, not until the dance evolves from a portrayal of a pig-hunt to a real hunt is there a horrifying murder.
But in the confusion of the night, the reader can anticipate that some shocking event may occur. In the case of the chant, true enough, 'the chant…began to beat like a steady pulse'.
'Roger ceased to become a pig and became a hunter' - this implies that a new prey has been found.
'There was the throb and stamp of a single organism'. The organism is in fact, the unified hunting circles moving as one, and the throb and stamp are the actions of the hunters in unison. This organism may be mistaken as a living creature but is in fact not.
'The dark sky was shattered by a blue-white scar'. The blue white scar, a terrifying strike of lightning, is metaphorically represented. Lightning striking in the sky is comparable to a scar on a forehead, and that is why this metaphor is very effective.
'The noise was on them like the blow of a gigantic whip' is a simile that is also effective. Readers can imagine a giant whip cracking, and this would be similar to violent thunder.
The noise ushers the boys on, and in the excitement of it all, they repeat their chant, louder than before.
The noise is repeated briefly after, and the repetition of a brutal and vicious statement like the aforementioned builds up a deadly and aggressive atmosphere.
'Him! Him!' - they have found their next prey.
'A thing crawled out of the forest' - readers will most likely realise that this 'thing' must be Simon, and will see the possible fate awaiting him. This mounts up much suspense and terror.
'The shrill screaming that rose before the beast was like a pain' - we can see that the boys believe this 'thing' to be the beast, and that they intend to hunt him down - 'the beast stumbled into the horseshoe' - Simon's fate is sealed.
The chant is repeated.
The scene that follows is grotesque and appalling. Simon is crying out, bringing the good news to the others, and they are trying to kill him.
Simon is referred to by Golding for the last bit as the beast, who 'fell to the sand by the water. The crowd surged after it, leapt onto the beast, screamed, struck, bit, tore.
The most disturbing element Golding has implemented is that his portrayal of Simon's murder is impartial i.e. it is not told with any mention of sufferance by Simon. It is simply the killing of the beast. That is how it is made so disturbing and horrifying.
