In Lord of the Flies, the beast represents fear, most children are afraid of the beast. In Lord Of The Flies the “beast” is just part of the children imagination and the beast is really fear in themselves. In Chapter 8 Simon is not really talking to the beast but part of his imagination and since he has fainted he is probably quite out of it.
The beast plays an important role in this book because if not for the beast most of the interesting parts of the story would take a while to get to or not happen at all. In the Lord Of The Flies there is many cases of the beast like the paratrooper and the sow head. The sow head is really the devil, Golding gives you this hint in chapter 8 when he talks to Simon and he says:
"This is ridiculous. You Know perfectly well you'll only meet me down there-so don't try to escape"
By the Lord Of The Flies saying this he is meaning that he will see Simon in hell or down at the beach were he is going to be killed by the other boys while they chanted and danced around him.