The Faithful (also called Elendili in Quenya and Nimruzîrim in Adûnaic, both terms meaning "Elf-friends") were those among the Númenóreans who turned aside from the policies of the later Kings of Númenor, and remained faithful to the will of the Valar. The opposing party was called the King's Men; it was composed of the majority of the people of Númenor in the later part of the Second Age, while the Faithful were a far smaller and increasingly oppressed group. They lived mostly on the west side of Númenor until Ar-Gimilzôr the twenty-third King commanded them to move eastward near Rómenna.
The Faithful became a party distinct from the King's Men during the reign of Tar-Ancalimon the fourteenth King. They maintained the use of the Elven tongues and welcomed the Elves of Tol Eressëa to their land, in spite of the growing hostility of the King's Men. The Faithful also respected and loved the Valar still, and made no attempt to speak against the Ban that the Valar had set against the Númenóreans sailing into the West. Nevertheless, they "did not escape the affliction of their people" regarding the fear of Death that the Shadow had brought upon all the Númenóreans, and they were troubled by the fate of Men. Unlike the King's Men, though, the Faithful had chosen to believe the words of the Messengers of the Valar and trust that death, called the Gift of Men by the Elves, was not an evil. It was in this choice that they differed most from the majority of the people of Númenor.
The Faithful looked to the Lords of Andúnië, a haven in the west of Númenor, for guidance in later days. These Lords, who were held in high esteem by all the Númenóreans, kept their connection with the Faithful a secret for a long time, because they wished to use their power in the King's Council to steer the Kings to wiser courses of action. Nevertheless, the rulers of the isle became increasingly antagonistic to all those who were recognized to be members of the minority party.
Like the King's Men, the Faithful also made settlements in Middle-earth, most notably Pelargir, but unlike them the Faithful did not seek to subjugate the natives of the Great Lands. Because of the coldness between the two parties, the Faithful built Pelargir far away from the colonies of the King's Men, which were a great distance to the south. The Faithful also sailed northwards to Lindon to converse with the Elves there.
The Kings of Númenor looked upon the Faithful and their continuing friendship with the Elves with increasing suspicion; they banned the use of the Elven tongues and eventually moved the Elf-friends to the east of the island so that they could no longer communicate with these "spies of the Valar", their name for the Eressëan Elves. The Kings even kept them under surveillance to make sure they did nothing subversive. The situation of the Faithful only became more bearable when Tar-Palantir, the son of Ar-Gimilzôr who was the greatest enemy of the Elf-friends, attempted to repent of the past actions of the Kings. He treated the Faithful kindly and allowed them to speak the Elven tongues again. But Tar-Palantir's rule was only a minor break in what would become an increasingly cruel policy of oppression, for his nephew seized the Sceptre after his death and proclaimed himself King Ar-Pharazôn.
Ar-Pharazôn did not immediately begin harassing the Faithful after he was secure in power; his attention was chiefly on Sauron, who had begun to assail the settlements of the Númenóreans with great strength. Angered by this, Ar-Pharazôn prepared a great military force and sailed to Middle-earth with the intention of defeating the Maia. When he arrived, the servants of Sauron fled in terror from his host, and Sauron himself surrendered to Ar-Pharazôn, seeing that he could not defeat the Númenóreans by arms. The King decided to take Sauron to Númenor as a hostage, and it was then that the worst of the Faithful's misfortunes befell them.
It was not long before Sauron had used his power to turn the hearts of most of the Númenóreans towards his counsels, and he told them that by using human sacrifices to worship Melkor, they could escape death. Naturally, "it was most often from among the Faithful" that the Númenóreans chose their victims for these sacrifices. They never said that they killed the Faithful for not worshipping Melkor, however; instead the Númenóreans accused them of plotting against the King and the rest of the people of the land.
This cruel treatment lasted several decades until Ar-Pharazôn grew old and was in great fear of the approaching end of his life. Therefore he listened to Sauron's suggestion that he gather a massive Armament and sail to Aman, land of the Valar, to claim everlasting life. When Amandil the last Lord of Andúnië heard this news, he knew that the Númenóreans would surely come to ruinous defeat in war against the Valar, and so he decided to make a preemptive voyage into the West to beg them for mercy and deliverance from Sauron. Before he left, he advised his son Elendil to furnish nine ships and anchor them off the east coast of Númenor and wait for what would happen next. After he sailed west, Amandil was never heard from again, but by taking his advice, Elendil and his sons survived the disastrous Downfall of Númenor that was the result of Ar-Pharazôn's war. A mighty wind took their ships eastward and swept them onto the shores of Middle-earth. There they set up the realms of Arnor and Gondor. These kingdoms were populated by both the descendants of the Faithful and indigenous Men of Middle-earth.