Endless
The Endless is a form of immortality created by the Preservation organization of the nation of Alexandria. In their society, when a person dies, their memories are artificially extracted from their soul and persist in an synthetic environment uploaded within "the cloud" of Living Memory. The Endless can take the appearance of their past selves. They do not need to fulfill any physiological functions such as sleeping and can freely teleport within Living Memory. Endless can also communicate in the outside world by remotely operating automatons or other vessels. Whether or not the Endless are considered "alive" is left up to the individual player's interpretation. Different NPCs have different opinions as well.
History
The Endless were created after the Storm Surge war devastated much of Alexandria's home reflection and killed the royal family. In particular, the apparent death of Queen Sphene from an overexposure to lightning aether resulted in a demand from the Alexandrians to preserve her memories so that she could continue serving as their ruler even in death.
Immense amounts of aether are required to sustain the Endless. Thus, it was Endless Sphene's goal to transport Everkeep to the Source and other reflections where she would harvest the aether from living beings of those worlds, at the cost of untold lives.
After Endless Sphene's defeat and the deactivation of the terminals within Living Memory, most of the Endless dissipated, although a few with particularly strong attachment continue to survive.
Notable Endless
Trivia
The continuation of some Endless after the events of the Dawntrail Main Scenario Quests may be a result of the game's attempt to explain why sidequest NPCs continue to exist, as it is logistically not feasible to make them inaccessible after completing the MSQ. The vendors in Living Memory are sentries probably for the same reasons.
Living Memory and the Endless strongly resemble the Holodecks from the Star Trek franchise. Also, many of the philosophical questions surrounding the Endless were addressed in Voyager with the Emergency Medical Hologram character.