The Faithful also known as Elendili or Elf-friends referred to the minority faction of Númenóreans who remained friendly with the Elves and respectful and obedient to the Valar. They were also called the Faithful for their continued devotion and obedience to the Valar. Their most noted leader was Elendil, Lord of Andúnië, who later founded the kingdoms of Arnor and Gondor in Middle-earth.
By the close of the Second Age Númenóreans had become split between the Elendili and the King's Men a faction centered around the King that sought to assert Númenórean authority and self-determination. With Númenor reaching the apex of its might, the King's Men eventually espoused open defiance of the Valar. This split would eventually precipitate the Fall of Númenor.
The Elendili, however, not only preserved their ancient friendship with the Elves, they also regarded the burgeoning arrogance of the King's Men as blasphemy, but the King's Men became more powerful, and by the end of the Second Age had begun to persecute the Elendili as rebels and dissidents. Fearing their growing strength, the King's men secured the Faithful's deportation from their strongholds in the western regions, notably around the city Andúnië.
The seeds of the Faithful were sown in the days of Tar-Minastir and Tar-Ciryatan; the group arose in the early twenty-third century of the Second Age during the days of Tar-Ancalimon with Andúnië as their chief city where the Elves were received with love. As use of Elven-tongues and respect for the Valar began to wane, the Faithful became the only ones to preserve these traditions unto themselves. In SA 2350 seeing the coming shadow, the Faithful founded the haven of Pelargir on the shores of Middle-earth as opposed to Umbar which became a haven of the King's Men. As the King's Men's influence grew and the people and their rulers became more and more greedy of wealth and power, there arose Ar-Gimilzôr in SA 3102. Being one of the King's Men, he openly persecuted the Faithful, forbidding the teaching and speaking of the Elven tongues nor was meeting with Elves permitted either. The Faithful were then forced to move from the west havens to Rómenna where they were carefully watched. In these evil days, many of the Faithful emigrated to the friendly havens in Middle-earth.
Some relief came to them in SA 3177, when Elf-friend Tar-Palantir assumed kingship and began to turn Númenor back to the ways of the Faithful. He repented the ways of his forefathers, stopped the persecution of the Faithful, and tried to amend the corruption of Númenor but his line failed and the King's Men survived. Tar-Palantir's nephew Ar-Pharazôn, son of Gimilkhâd forcibly usurped the throne and the Elendili were more vigorously oppressed. He defeated Sauron, the Dark Lord and took him prisoner to Númenor. It was not long before the King listened to his evil words and took him deep into his councils, Sauron playing off his fear of death. This time with the help of the Dark Lord Sauron, who had established an evil cult on the island to corrupt and eventually destroy Númenórean society.
It was during these dark times that the Faithful endured their most grievous woe for the King. During this time the Faithful were hunted, killed and even sacrificed in Sauron's temple to the cult of Melkor. When the King prepared the Great Armament, Amandil, the current leader of the Faithful attempted to sail to Aman to beg for forgiveness and mercy from the Valar. Before doing so, he entrusted his son with the task of preparing a fleet of ships to depart to Middle-earth to escape the coming darkness. As Ar-Pharazôn led his grand armada to Aman to challenge the Ban of the Valar, Elendil and the remaining, Elf-friends were warned by the divine powers to leave Númenor forever. They were thus spared the downfall of Númenor when, as punishment for an attempt to defy the Ban, Eru Ilúvatar sank the island kingdom into the sea.
When Númenor was destroyed in SA 3319, the fleet reached the shores of Middle-earth founding the kingdoms of Arnor and Gondor in a lineage of nobility leading up to king Elessar. The Elendili, under the leadership of Elendil and his sons, eventually made their way to refuge in Middle-Earth where they were welcomed by the Elves.