Each Eldar Craftworld has its own unique style of martial forces, whether by choice or circumstance. Below are some guidelines on how to use the rules in Codex: Eldar to represent an army of each of the various Craftworlds.
(Iyanden is not included as it already has a supplement with specific rules for it.)
The Alaitoc craftworld relies upon the large number of Rangers who originate from the Craftworld. These Rangers scout out possible trouble spots, enemy worlds, Maiden Worlds, and scout ahead of the main force in battle. Alaitoc Rangers are trained to be self-sufficient, to know when and how to fight. The Alaitoc craftworld relies on its Rangers to give it forward knowledge on locations they are moving toward.
Any compulsory Troops choices in an Alaitoc army should be filled with Rangers, before selecting any other forces. As Alaitoc is a quick-strike Craftworld, it’s recommended that you avoid Wraithknights and grav-tanks.
The Biel-Tan craftworld has a large number of Aspect shrines, as it places great faith in the Path of the Warrior. They have a much larger force of Aspect Warriors to fight for them than other craftworlds do, and thus their armies have less need for the artisans, farmers, and other Eldar to take up arms as often. In battle these armies of Aspect Warriors are extremely deadly.
A Biel-Tan army should have no Guardian squads or Windrider Jetbike Squads. Instead, it should use Dire Avengers, Striking Scorpions and Shining Spears in their place.
The Saim Hann Crafworld employs the use of a large number of jetbikes and skimmers. In battle they use these skimmers to make fast hit and run attacks against their enemies, slashing at them with lasers, shuriken, and plasma fire. The crafworld is also know for its Wild Riders – jetbike riders who are very skilled and very deadly. The Wild Riders swoop down upon their foe relentlessly, destroying them with massed shuriken fire.
Any compulsory Troops choices in a Saim Hann army should be filled with Windrider Jetbike Squads. Wraithlords and Wraithknights are very much discouraged; used grav-tanks in their place. All characters should be mounted if possible, and Aspects should have transports.
Ulthwe lies close the Eye of Terror, a dire realm inhabited by many vile followers and creatures of the Chaos Gods. Ulthwe has many Farseers to quide it through the strands of the future, and many Eldar of Ulthwe follow the Path of the Warlock. These Farseers and Warlocks must constantly fight off the forces of Chaos. Ulthwe is constantly in danger of being overwhelmed, by Chaos, by Orks, by the Imperium, and by another threat… the Sleeping Ones. The craftworld seems almost damned to its destiny, a destiny of destruction.
An Ulthwe army will always be led by a Farseer and a Warlock Council.