Stone of Osgiliath
The Master Stone of Osgiliath was, presumably, the greatest of the seven palantíri that the Faithful brought to Middle-earth from Númenor. It was also the only palantír that could be used to secretly listen to communications between the users of the other palantíri.
The Master Stone of Osgiliath was, presumably, the greatest of the seven palantíri that the Faithful brought to Middle-earth from Númenor .