Craftworld
Craftworlds are massive, self-sufficient Eldar vessels, essentially mobile cities made of Wraithbone flying through space.
History
During the height of the Eldar Empire, the Eldar built the Craftworlds as large merchant ships. Somewhat questionably for traders, they didn't install any sort of Webway or Warp drives on the Craftworlds, instead forcing the Craftworlds to travel at sublight speed. Ultimately, this would be to the Eldar's benefit, for the amount of time spent between Eldar worlds allowed the Eldar on the Craftworlds to see just how far their people had fallen into hedonism. Realizing that something bad would happen soon, the Craftworld Eldar evacuated the Eldar still sane enough to realize how far they'd fallen from their depraved brethren, and fled, taking with them the repositories of Eldar history, science, and religion.
Unfortunately, Not all of them made it out of the Segmentum Obscuris in time, and were caught in the creation of the Eye of Terror just as the hedonists were. So grimdark.
Today, the Craftworld Eldar comprise the largest populations of surviving Eldar. They have similar goals in preserving the Eldar, reestablishing their Empire, and fighting Chaos. However, the Craftworlds often disagree over how to achieve these things. This can lead to small conflicts between the different Craftworlds, but for the most part these are rare.
Tabletop
Back in the third edition of Warhammer 40,000, Games Workshop released Codex: Craftworld Eldar, a "mini-dex" expansion booklet for the Eldar codex. It included five army list variants for the craftworlds Alaitoc, Biel-Tan, Iyanden, Saim-Hann, and Ulthwe. Each Craftworld receives a few unique units, and some receive army-wide special rules, a re-assignment of the available squads between the various categories (Troops, Elites, etc.), or even a different force organization chart. In the later Codex: Eye of Terror (released for the 2003 "Eye of Terror" summer campaign), Ulthwe got another mini-list for their "Strike Force".
Unfortunately, the Eldar got hit with the "less-is-more" bat in Fourth Edition, so the only difference between the Craftworlds on the tabletop nowadays is that they have different colors and symbols.
Notable Craftworlds and specialties
- Alaitoc -- Follow the Eldar Paths more strictly therefore Eldar of Alaitoc have less fun. This leads them to become arrogant outcasts and eventually become veteran rangers and pathfinders.
- Biel-tan -- Wish to reclaim the old Empire of the Eldar before it got screwed over. Almost everyone is arrogantly warring.
- Iyanden -- Got OM NOM NOM NOM'd so almost everyone is dead.
- Saim-Hann -- Everyone here loves jetbikes that are swift.
- Ulthwe -- They're a few inches away from the bleeding asshole of reality (which is why its nicknamed "Ulthwe the Damned") so everyone is extensively trained for war, even the regular Guardians, who are called "Black Guardians". Also, this is where that dick was born.
- Malan'tai -- Got LOLDRAIN'D by a unique Zoanthrope who feeds off psychic energy. Needless to say, after it devoured the souls on the Craftworld's Infinity Circuit, things went very bad for them.
- Kher-ys -- Destroyed by a Slaaneshi daemon incursion. Ohh, and a Keeper of Secrets possessed their Avatar during the fighting, you can imagine how much proverbial buttrape happened there.