What does Simon do to the figure on the mountainside?

When Simon wakes in Chapter 9, he is weak from his seizure and resulting blood loss. He wanders through the jungle seemingly at random, and eventually comes to the "beast from air": a parachutist who has been killed in the war, and landed on the island. Simon is disgusted by the figure, which is covered in flies exactly like the pig's head. He is revolted just like the other boys; perhaps more so because he understands the truth behind this grotesque thing. He forces himself to look however, forces himself to know the meaning of the beast.

The tangle of lines showed him the mechanics of this parody; he examined the white nasal bones, the teeth, the colors of corruption. He saw how pitilessly the layers of rubber and canvas held together the poor body that should be rotting away. Then the wind blew again and the figure lifted, bowed, and breathed foully at him. Simon knelt on all fours and was sick till his stomach was empty. Then he took the lines in his hands; he freed them from the rocks and the figure from the wind’s indignity.

So after witnessing the parachutist, and becoming physically sick as a result of it, Simon finally untangles the parachute lines from the rocks, and sets the figure free. It is one less representation of evil on the island, and Simon is excited by his discovery. Of course, as he races to tell the other boys, they mistake him for the beast, leading to his tragic death, and the breakdown of all order on the island.