Exodite

The Exodites are civilian Eldar who are not aligned with the Craftworlds or the Dark Eldar. They're basically Amish dinosaur-cowboy Wood Elves In Space, and very like the Na'vi from James Cameron's Avatar.

The Exodites originated from those citizens of the Eldar Empire who saw the corruption festering in the souls of the Eldar and decided they needed to purify themselves. To do so, they left the Empire and its conveniences for worlds on the edge of the galaxy (an exodus, hence "Exodites"), where they would be forced to work hard just to survive. This kept them focused and busy, and prevented them from being lost in hedonism like their relatives back home. When the Empire's increasing debauchery gave rise to Slaanesh, the Exodites survived because they were far from the center of the Empire (what would later be called the Eye of Terror) and because their hard lifestyle and self-denial meant that Slaanesh had little purchase on their souls. Of course, the Eldar idea of "hard lifestyle and self-denial" means that they have to walk a few feet to pick up their own damn food instead of it appearing before them automatically, though it still grows flawlessly for them and every plant and animal on the planet caters to their every need and whim. They probably wouldn't last five seconds on real life Earth. Apparently, they are not completely free of Slaanesh's influence; when they die, their souls are stored and contained in their planet's World Spirit (analogous to the Infinity Circuit of the Craftworlds).

As of the 41st Millennium, the Exodites still keep to themselves, though the expansion of the Imperium of Man and the encroaching Tyranid Hive Fleets have brought them into conflict. They defend themselves with their dinosaur-riders, and Craftworld Biel-tan often dispatches forces to aid Exodites under attack. Though in Black Library books Exodites are describes as absolute badass and comparable to the Catachan, they likely do not need any help to beat the shit out of anyone stupid enough to invade their world. In one book they almost effortlessly repelled combined four cabal raids (to be said, all four was from "Comorragh top ten") and in other, one entire THREE pre-heresy Space Marine Legions was needed to conquer single Exodite world. That kind of badass though the Imperium arguably had more advanced equipment than what the Exodites denied to themselves. It should be noted that the only reason for this is not due to any particular skill of the Exodites, but rather, as depicted in the book "Deathworld", an Exodite world becomes Catachan on crack towards any invaders. The Exodites need only hide and perform (likely suicidal) hit-and-run attacks on invading convoys and supply depots while letting the planet itself do the rest. Of course, there's a fine and dandy way of solving that little issue.