Set in the Tower of Amon Sûl at the heart of Arnor, the Stone of Amon Sûl was said to be the most powerful of the three possessed by the Northern Dúnedain. It was larger than most of the palantíri: so large, in fact, that it could not easily be transported, and so it remained set in its Tower throughout the early centuries of the Third Age.

When Arnor broke up into three lesser realms, the Tower of Amon Sûl marked the point where the three new kingdoms met, and there was much conflict over the ownership of the powerful Stone. The Tower was ultimately destroyed by the forces of Angmar, but its Seeing-stone was rescued and carried away to Fornost. Centuries later, Fornost itself was overthrown by the Witch-king, but the Stone of Amon Sûl was rescued once again, and carried into the north by Arvedui and his companions.¹ It was finally lost when Arvedui took it aboard an Elven-ship that foundered in the Icebay of Forochel.