The son of King Ar-Gimilzôr of Númenor and his consort Inzilbêth. Inziladûn was secretly raised by his mother in the ways of the Faithful, that party of the Númenórean people who remembered their years of friendship with the Elves and respect for the Valar. When Inziladûn succeeded his father to the Sceptre, he attempted to return Númenor to those old ways, halting the oppression of the Faithful, and recommencing the tradition of the Three Prayers that had long been abandoned.
As a reforming King, Inziladûn took the Sceptre in the name of Tar-Palantir, meaning 'The Farsighted', but his younger brother Gimilkhâd was of quite different mind. The strife between them was such that Tale of Years describes Tar-Palantir's reign as 'civil war'. Inziladûn's restoration of the old ways did not last long: after his death, his daughter Míriel was forcibly taken as wife by Gimilkhâd's son Pharazôn, who thus usurped the Kingship and began Númenor's final decline.