How would portray this third group of Eldar?

I am thinking of using what is in RT for the Eldar already and just using the Psyker Archetype as a basis. More than likely keep them Slaanesh aligned.

How would you have them look? More bare chested with tattoos and other psychic defenses or to the extensively baroque suits of armor and brightly colored so they can experience a full array of sensation. I see their mutations being far more subtle to enhance that natural grace and allure of the other Eldar. Only the most dedicated leave the Crone Worlds to enact the will of Slaanesh to bring back their cousins to the embrace of the Dark Mother. A corrupt Eldar ship with the most terrible technologies of the Eldar at their height with the reality bending techno-sorceries of the Warp. How would you display their ships?

I also see them being allies of the a Heretic Coven since they serve the Dark Gods, even more so if that Heretic is aligned to Slaanesh.

One more thing, Slaanesh specific powers for the Crone World Eldar?

Bit hard to say, the material contradicts itself in regards to the Crone Worlds over the years, back in I think 4th ed there was a few sentances that a few ancient eldar existed, trapped there after the fall and used as Slaanesh's bitch/chewtoy. But mostly it will also say that everyone who wasn't on a craft world, hiding in the webway or on an exodite world- got consumed at the time of the big bang.

I would say, if they are there in your game, those remaining would have to be championing one of the chaos powers and not necessarily Slaanesh, who they could have out of spite turned to Nurgle or Khorne, or even Tzeench to dodge the fate of their fellows. Once you've got the tramp-stamp of a major power its hands-off and you simply become a moving target for the opposing powers.

Mutations & appearance… as much as anything else (short of a necron or ork) stuck for 12,000 years in the middle of a warp storm on a Daemon world! Probably mostly unrecognisable as an Eldar, which is a valid enough reason why there hasn't been any real sitings of them since the fall, put a green frog in a blender and it'll mostly end up looking the same as a red frog in a blender. Chaos, the great unifying force in the galaxy making everyone regardless of species or race, looked just as f**ked up and acting crazy as the next guy :) 

By its nature, wraithbone equipment holds and channels souls fairly well, so it should also be a place to drop a daemon or two in there and remembering, the core-eldar worlds where some of the most advanced ones in the galaxy in terms of technology and power. So instead of your armour being powered by the memories of your ancestors, its powered by satan

MKX said:

Good summery. If I was to make a Crone World Eldar I would probably make him as any other character in BC but possibly gift him with some unnatural Agility and Intelligence and possibly some Psy related stuff. But except for that it's probably just to go as you would make a human.

As far as appearance, I picture them as being very much like daemonettes.