Ariel is a spirit who works in Prospero’s service. Prospero first encountered Ariel soon after landing on the island. He found Ariel trapped in a cloven pine tree and freed the spirit from his prison. In return, Ariel promised to serve Prospero faithfully for a year, after which time Prospero would give Ariel back his freedom. We don’t know how long Ariel has already worked for Prospero when the play begins. Prospero has been on the island for twelve years, so Ariel might have been in his service for many more years than their agreement required. Then again, possibly Prospero freed Ariel from the tree only a year prior to the events of the play. Either way, Prospero’s unwillingness to set Ariel free stems from the fact that Ariel possesses immense power. As the spirit explains in his first lines in the play, not only does he have an impressive range of abilities, but he also commands a host of lesser spirits. Given Ariel’s extraordinary magical abilities, Prospero leans heavily on him to execute his complex revenge plot. Ariel has spent a lot of time around humans and he learned a thing or two about them. In Act V, for example, he appears to take pity on the castaways. He tells Prospero that if he were human his “affections” would be “tender,” convinces Prospero to stop using magic and reconcile with his enemies. Ariel effectively manipulates Prospero by appealing to his humanity, and in doing so he ushers himself closer to freedom.