how does darkness change throughout the book?

Darkness changes from the environment into the very souls of most of the boys. In the early chapters, Golding concentrates on the darkness of the jungle and their terrors at night. By the end of the book, Simon's vision of the beast, "a human at once heroic and sick", is manifested in most all of the boys on the island. Just consider the horrid things they do. The Pigs head on the stick also solidifies Golding's idea of the darkness which lives in them all.