Prospero is the rightful duke of Milan but then Antonio his younger brother took his place as the duke of Milan. He is helpless against his enemies until they appear on a ship but when they are close enough, he can use his magic to create a storm and bring them under his control. Although he refuses to free Ariel and enslaves Caliban, Prospero is really a beneficent ruler, never trying to injure even his enemies. Also, Prospero tests Ferdinand to see if he deserves his daughter Miranda because Ferdinand wants to marry her.Prospero also calls Antonio a traitor for taking over his thrown as the duke of Milan.