At the beginning of the Second Age, when the Númenoreans began to settle into their land, the Valar issued a Ban, forbidding the Dúnedain from setting foot on the Undying Lands or sailing into the west out of sight of Númenor’s shores.
Initially, the Edain respected the ban, and were content to explore regions elsewhere; but as their power grew, so, too, did their jealousy. Ar-Pharazôn, the twenty-fifth and final King of Númenor, began to speak out openly against the Valar and the Ban. Believing that by visiting the Undying Lands, the Númenoreans could achieve the immortality which the Valar had been denying them, Ar-Pharazôn took a fleet into West and tried to invade the Undying Lands. The Valar laid down their guardianship of the world, and Númenor was devoured by the Sea.