Jack makes the beast into a godlike figure, a kind of totem he uses to rule and manipulate the members of his tribe. He attributes to the beast both immortality and the power to change form, making it an enemy to be feared and an idol to be worshiped. The importance of the figure of the beast in the novel cannot be overstated, for it gives Jack’s tribe a common enemy (the beast), a common system of belief (their conviction that the mythical beast exists), a reason to obey Jack (protection from the beast), and even a developing system of primitive symbolism and iconography (face paint and the Lord of the Flies).
Parachute man' s disappearance may have some effect on Jack's control of the boys. Fir as long as he's able to convince them that it's the beast (from a distance), he has a certain hold because they're afraid. Without it, that hold may dissipate.