Prospero uses his magic to control Ariel and Caliban. He does this to do several things. First, he uses it to establish a kind of hierarchy on the island, with him on top, and the enslaved spirit and creature below. Second, he makes the savage Caliban into a servant. Third, he uses his magic to generate the storm that destroys the ship in the first scene. Fourth, once the men are on the island, he uses magic to create illusions and otherwise manipulate them. He does all this to produce a situation in which those who were shipwrecked will realize the evil of their ways, and eventually, bring him back to his rightful place.