Eldar are humanoid and look very much human, but are distinguishable by their slender build and pointed ears. They are -- for all practical purposes -- space elves.
Eldar have extremely long life expectancies, high metabolisms, and superhuman speed and agility. All Eldar possess some level of psionic ability, ranging from basic telepathy to powerful psychokinetic powers and precognitive abilities. In potential, they are among the most powerful psionics the galaxy, but they are largely unable to utilize these abilities (see History). Psychologically, Eldar are prone to emotional extremes, a trait that directly contributed to their downfall.
Due to the circumstances of the fall of their civilization (see History), the souls of the Eldar are vulnerable to the Chaos god Slaanesh. To avoid having their souls entrapped, Eldar wear psionic devices called Soul Stones that contain their souls when their bodies die. The souls in the stones remain sapient, and the stones can be installed in various kinds of Eldar equipment as advisors, operators, or both.
The Eldar were once the dominant species in the Warhammer 40,000 universe with a galaxy-spanning empire. Decadence began to spread in Eldar society, however, and various cults emerged dedicated to experiencing everything the world could offer, beginning with simple hedonism and then moving towards cruel and sadistic rituals involving torture and murder. These acts and those who died from them sent out powerful psionic emanations into the Warp that coalesced over time to form the Chaos god Slaanesh. The birth of the new Chaos god wiped out most of the Eldar civilization, laying waste to the worlds at the core of their empire and leaving only scattered remnants.
The remains of the Eldar civilization live mostly as refugees on massive spacecraft called Craftworlds. Among the more notable of Craftworlds are...
Craftworld Eldar tend to revolve through an array of different professions or "Paths" during their long lives. One of these professions is the Aspect Warrior, in which the Eldar explores various aspects of the Eldar war god, Khaela Mensha Khaine. Obviously a variety of non-combatant professions exist, including Bonesingers, who shape the material known as Wraithbone that is widely used in Eldar construction.
Eldar military forces are divided up into various groups. Most Eldar adopt the Path of the Warrior during some portion of their lives, and in time of need, former Aspect Warriors return to service as Guardians (comparable to modern military reserves or national guard forces). Guardians make up the bulk of the military assets that the Eldar have at their disposal. The active-duty Aspect Warriors handle missions that don't require the full mobilization of a craftworld.
Eldar society is often led by precognitive figures known as Seers and Farseers who plan group action specifically to protect the group's members from Chaos, especially Slaanesh.
A few Eldar -- who call themselves Exodites -- have settled on former frontier worlds of the Eldar empire which were being terraformed when the Eldar civilization fell and have since become inhabitable. Exodite Eldar function with limited technology and often come into conflict with Human Civilization.
A small subgroup of Eldar have dedicated themselves to the Eldar Laughing God (the only other Eldar god to have survived the birth of Slaanesh) and have dedicated themselves to eradicating Chaos; they are known as Harlequins.
Finally, a renegade faction of Eldar descended from the pleasure cults that brought about the Fall still exist; these are known as the Dark Eldar.
Despite their small numbers, the Eldar remain a surprisingly powerful faction in the Milky Way galaxy. They have superior technology to that of the Imperium of Man, more experienced psionics, and a safer method of FTL travel than most other factions through their Webway. In particular, the precognitive powers of their Farseers allow them to use their limited resources to maximum effect.
Although they possess considerable power, the Eldar will usually ignore other races unless they feel their own survival is threatened. In war, the Eldar are utterly merciless and consider all other races to be inferior. They will wipe out entire populations of other races if doing so means protecting the lives of a few Eldar. On rare occasions, they will aid other races if they have no other choice (having sometimes aided the Imperium against the forces of Chaos) and a few individual Eldar are somewhat more willing to be cooperative, but the Eldar's prejudice towards other races makes it unlikely that they would form a lasting alliance with "Monkei".
Eldar of Note
- Farseer Eldrad Ulthran: Eldrad Ulthran was, until his recent death, the leader of Ulthwe Craftworld. He is said to have provoked the second Armageddon war (a conflict in which millions died) to spare the lives of 10,000 Eldar.