1. The beast makes a dramatic appearance in chapter six in the form of the parachuter who drifted onto the mountainside and consequently scared Samneric. The beast symbolizes the boys' fear of the unknown on the island. This entire time they have been debating its existence, worrying if it was a 'snake thing' or something from out of the water, and the bulging silhouette of the parachuter seems to confirm that all of their worst fears have been realized.
2. Castle Rock-- The boys visit Castle Rock at the end of the chapter, but the rocky fort leaves a strong impression on Jack who sees its great strategic potential. As the novel progresses, Castle Rock will become a symbol of Jack's power when he declares himself chief, but also one of savagery. As Jack delights in the easily rolled boulders on their first trip there, one of those boulders will end Piggy's life. With Jack in charge and the emphasis on hunting instead of rescue, Castle Rock ultimately becomes the boys' new home, symbolizing their complete turn from civilization.