In T.A. 1409 the watchtower was burned and destroyed when Angmar's forces invaded Arnor. Arthedain's last King, Arvedui, saved the palantír as well as the Annúminas-stone,when Arthedain was overrun by Angmar in Third Age 1974.
With these and other heirlooms, he fled into the far north, where he was given shelter by the Lossoth. At last a ship from the Grey Havens came to rescue Arvedui, but after he had boarded, its hull was crushed by the ice, and all aboard were lost. The Stone of Annúminas, along with that of Amon Sûl, were lost in the shipwreck, and sank.