The Master-stone was the highest of all the Palantíri.
The Master-stone was no doubt made at an unknown time by the Ñoldor prince Fëanor while still in Aman. Exactly where it was during the rest of the Years of the Trees and the First Age has not been recorded. It is only mentioned in the history of the Dúnedain in the time of Elendil's rule of the exile kingdoms of Arnor and Gondor in Middle-earth after the Fall of Númenor, as being in the Tower of Avallónë on Tol Eressëa in the Undying Lands. It is recorded that Elendil, while using the Elostirion-stone to gaze into west was believed to have been able to see the Tower of Avallónë where the Master-stone was kept.