The eldar are a race of elves that had to flee from Eberron in ages past to live on the astral plane. Over several generations had passed the eldar that developed many strange powers. Over generations the eldar civilization continued to grow in size and some of the eldar left to form other city-states, these city-states that are called Craftworlds by the eldar, and they float in the astral plane. The major craftworlds that are known are Biel-Tan, Iybraesil, Mymeara, and Ulthwe.
The bulk of each craftworld is protected by what is known as guardians who provide most of the defense and attacking of foes, but each craftworld is protected by an elite force of aspect warriors. Each of these Eldar warrior clans that both provide defense and attack are different from one another as night and day. These various warrior clans that preside within the craftworlds, they are known by these names Dire Avengers, the mysterious Harlequins, the deadly Howling Banshees, the ghostly Shadow Specters, the swift Shining Spears, the shadowy Striking Scorpoions, the swift Swooping Hawks, the mysterious Warp Spiders, and the immoveable and deadly Wraithguard. The one thing that is the most important for each of these craftworlds, is that while each craftworld is different, all craftworlds are led by a mysterious Warlock Council and the leaders of these councils the powerful but mysterious Farseers who are among strongest psykers and mystics of the Eldar race.
But in every society there are still outcasts. These outcasts from various craftworlds will generally form bands of reavers to haunt the astral plane, these revers will then roam the astral plane to plunder various city-states at will. Many a astral domain thought they where being visited by graceful voidships of the elven fleet, but are astonished to be attacked by reavers, looking for plunder and slaves. The Eldar have a name for these reavers, they call them the Dark Eldar.
Eldar weapons and voidships are works of art that make the best mastercrafted items of other races look like poorly made toys by comparsion.