The Deathless

Death was originally a Gift granted by Ilúvatar to Men, and shared by other mortal races, but there were many beings in Arda for whom death was unknown. Those Ainur who descended into the world at its beginning were immortal by nature, and so were the Firstborn Children of Ilúvatar, the Elves, who were bound to the world until its end. The Valar and Maiar made the land of Valinor in Aman in the West, and many of the Elves also travelled across the Sea to dwell there. Thus the lands of the West beyond the Sea became known as the Undying or Deathless Lands, and the people who lived there were known as the Deathless.

There were Deathless beings in Middle-earth as well as Aman, most notably those Elves who had remained behind, or had returned across the Sea to mortal lands. These beings did not age, but if they remained in the lands eastward of the Great Sea they would eventually fade to little more than spirits. Though these beings were Deathless, they were not immune to harm - they could be slain, and if they were, their spirits would return to the Halls of Mandos in Aman, ultimately to be given a new life in the Deathless Lands.