Ariel is a spirit in William Shakespeare's play The Tempest. Prior to Prospero arriving on the island, Ariel had been a servant of Sycorax. Ariel was imprisoned by the sorceress for not obeying the commands she gave to him. By the time Propsero releases Ariel from his pine tree prison, he has been in the tree for twelve years. Unfortunately for Ariel, Prospero makes him his servant immediately upon releasing him.
Prospero orders Ariel to command the winds so that Alonso and his crew become stranded upon Prospero's island. Ariel must continue to obey Prospero--convincing Alonso that his father has died and making him fall in love with Prospero's daughter, Miranda. Ariel does prove to be self-thinking: he saves Alonso from an assassination and Prospero from being overthrown by members of Alonso's group.