Who turned into a harpy in the tempest?

In Shakespeare's play "The Tempest," the character who turns into a harpy is Ariel, a spirit who serves the magician Prospero. In Act 3, Scene 3, Ariel appears as a harpy to confront and chastise the shipwrecked nobles, revealing their past wrongdoings and the consequences they must face. This transformation symbolizes both Ariel's magical abilities and the theme of justice within the play.