Meanwhile, the Ents, roused by Merry and Pippin from their peaceful ways, attack Isengard , Saruman's stronghold, and trap the wizard in the tower of Orthanc . Gandalf convinces Treebeard to send an army of Huorns to Théoden's aid. Gandalf brings an army of Rohirrim to Helm's Deep, and they defeat the Orcs, who flee into the waiting shadow of the trees, never to be seen again. Gandalf offers Saruman a chance to turn away from evil. When Saruman refuses to listen, Gandalf strips him of his rank and most of his powers. Pippin picks up a palantír , a seeing-stone that Saruman used to speak with Sauron and through which Saruman was ensnared, and is seen by Sauron. Gandalf rides for Minas Tirith , chief city of Gondor, taking Pippin with him.