What threat does the Lord of the Flies make to Simon?
Toward the end of chapter 8, Simon encounters the Lord of the Flies, which is the severed pig's head that speaks to him about the true identity of the beast. The Lord of the Flies initially tells Simon to run along and play with the other boys because the beast is not something that he will be able to kill. The Lord of the Flies then speaks with an authoritarian tone and threatens Simon, warning him not to escape. The Lord of the Flies proceeds to tell Simon that the boys are going to have fun and there is nothing that will stop them. It then threatens Simon by saying,
"I'm warning you. I'm going to get angry. D'you see? You're not wanted. Understand? We are going to have fun on this island. Understand? We are going to have fun on this island! So don't try it on, my poor misguided boy, or else . . . Or else," said the Lord of the Flies, "we shall do you? See? Jack and Roger and Maurice and Robert and Bill and Piggy and Ralph. Do you. See?" (112)
Essentially, the Lord of the Flies threatens Simon not to escape or try to prevent the other boys from having "fun," which is synonymous with acting like unrestrained, morally degenerate savages. The Lord of the Flies hints that Jack, Roger, Maurice, and the boys will kill him if he attempts to ruin their fun.
In simplest terms, the Lord of the Flies threatens Simon with the charge that he, Simon, will be seduced by the evil and savagery within himself just like all the other boys on the island. Furthermore, the LotF tells Simon that there is nothing Simon can do stop the snowball effect of savagery.
The Lord of the Flies announces to Simon that he is a part of Simon, a part of all the boys. He foreshadows the end of the story by demonstrating that the boys characters are too flawed to be able to overcome anarchy.