The first one is very simple, it is the nature. Ralph and other boys were left on a small island after the plane they were on crushed. The nature is the first thing that the boys need to face. It is the first of all they need to come over in order to survive. This made the boys very cooperative at the beginning. After the boys are used to live on the island, the thing started to turn worth. The hunters are used to kill. They are not hunting the animals for the meal of everyone anymore, but hunting to satisfy themselves.
The second challenge is the mind of the boys. As the last paragraph said, the hunters began to hunt for fun instead for everyone’s meal. The boys themselves are getting succumbed into the more interesting but less moral things. The Lord of the Flies (the pig head) said that he is inside everyone’s mind, which means the beast that everyone was afraid is actually themselves.
The third challenge is the boys that couldn’t come over with the second challenge. Near the end of the story, only Ralph, Piggy, and a few littluns (including Sam and Eric) didn’t join Jack’s tribe. All the other boys were attracted by the freedom and fun they thought Jack’s tribe would be. Jack is the leader of this force. He acts like a tyrant in his tribe that he beats up other boys without any reasons, and he doesn’t let other boys to give suggestion in the assembly.
These forces are the major factors that caused the tragedy of Piggy and Simon. Under the special situation, many boys couldn’t keep their intellect and turn into savages. Ralph is the only boy who didn’t join Jack’s tribe and survived until the end.