The Númenóreans became great seafarers, and were learned, wise, and had a lifespan beyond other men. At first, they honored the Ban of the Valar, never sailing into the Undying Lands. They went east to Middle-earth and taught the men living there valuable skills. After a time, they became jealous of the Elves for their immortality. Sauron, Morgoth's chief servant, was still active. As Annatar, in disguise he taught the Elves of Eregion the craft of creating Rings of Power. Seven Rings were made for the Dwarves, while Nine were made for Men who later became known as the Ringwraiths. However, he built a stronghold called Barad-dûr and secretly forged the One Ring in the fires of Mount Doom to control the other rings and their bearers. Celebrimbor, a grandson of Fëanor, forged three mighty rings on his own: Vilya, possessed first by the Elven king Gil-galad, then by Elrond; Nenya, wielded by Galadriel; and Narya, given by Celebrimbor to Círdan, who gave it to Gandalf.