Fëanor forged the eight Seeing-stones during the Elder Days. The palantírs are described as perfectly round spheres, varying in diameter, and very heavy. They were mainly used as Seeing-stones since they enabled their owners to see far and wide, but, as always, there were certain limitations. Some of the lesser palantírs could not see into the great distance, and many palantírs display only what is near another palantír. Only those strong enough can use the palantírs whenever they wish and point them in any direction. Since the visions seen in the palantírs could hardly be controlled, it was said that they can only be used properly by the heirs of Elendil.
During the events of the War of the Ring, the palantírs were especially dangerous to use, because they were all under Sauron’s control. They were scattered all over Middle-earth, in strategic places, where Sauron could gain the most from controlling them. The Master-stone was kept in the Tower of Avallónë, the Lonely Isle of the shores of Valinor. Three palantírs were located in Annúminas, Amon Sûl, and the Tower Hills in Arnor, the three locations known as the Númenorean realms-in-exile, and the remaining four were kept in Osgiliath, Orthanc, Minas Ithil and Minas Anor. Denethor II, the Steward of Gondor, frequently used one of the palantírs, and with time it corrupted him, he became paranoid and obsessed with acquiring vast knowledge, to surpass his father, and even Gandalf. However, the palantír Denethor II used followed him into his death, when he set himself on fire, still clutching it in his hands. The only one who could wield the palantír and use it properly was Aragorn, the heir of Elendil.