So a common question between Space Marine players -- a majority in these parts -- is why you picked your Chapter/Legion. My question for this new section, then, is why did you pick your Craftworld?
Mine is that of Altansar. The last Craftworld to depart the Empire before the Fall and survive it, the fate of Altansar was a question for thousands of years. The only known survivor was a great and terrible warrior who would become one of Asurmen's first students: Maugan Ra, the Harvester of Souls, Phoenix Lord, and father of the Dark Reapers.
I started my Eldar army shortly before the Eye of Terror campaign commenced and was yet undecided as to which Craftworld I should devote my allegiance. I did know, however, that Ra was simply the baddest-ass of the Phoenix Lord. His model is so unlike the rest of the line, swapping smooth lines and an almost aerodynamic physique for a monstrous build (for an Eldar; seriously, he's a beefcake!) and the most awe-inspiring suit of armor I have ever seen on a 40K model. I knew that whatever Craftworld I ended up painting my army in, Ra was going to lead it. Then Codex: Eye of Terror dropped and we come to find out that Ra has led a strike force Ulthwe Black Guardians, backed a veritable army of Reapers, into the Eye to find his lost home and guide it back into realspace. He does successfully, and now while the Altansarai are outcasts even among their own kind, they have thrown themselves into beating back the forces of Chaos.
It's a great back story. The possibly corrupted -- we don't know, they won't unhelm in the presence of outsiders -- Eldar have returned from exile within the Great Eye. Despite long exposure to the Warp, in the physical afterbirth of She Who Thirsts, they remain pure of heart and devoted to defeating Chaos. Yet even their fellows of darkly-famed Ulthwe barely trust them. It's a perfectly grimdark tale and, combined with the sheer bleeding awesomeness that is Maugan Ra, that's why I chose Craftworld Altansar.
So what about you?