Amon sul was an important watchtower in Arnor that held one of the seven palantiri. After the division of Arnor into three separate kingdoms Amon Sul was contested amongst the realms. In the early days of the Angmar War Amon Sul would be razed to the base of the hill. In the ruins of Weathertop Frodo would be stabbed with the Morgul knife.

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History of Arnor:    • The Kingdom of Arnor