The Red Walkers

The Red Walkers are a mysterious group that makes their home within the Rust Garden, and are the only group to do so. At least, the only group to do so and not be killed off in short order.
While it's known that they're a baseline human group, and not a type of Drift, very few people have seen their faces. Given their home, this makes sense, as they must remain heavily covered to keep the skin from being stripped from their bones.
If you do see them, a rarity in and unto itself, the most notable thing you'll see is the red woven fabric that they use to do the aforementioned covering of most of their body. Thick and heavy, it's comparable to leathers when layered correctly. It is intricate stuff, and one of the only things the Walkers willingly trade with outsiders. It's red and gold coloration making all of the Walkers look rather refined, despite being nomads who live in one of the most dangerous places on Mother Earth. 
They may be willing to trade their cloth and fabric, but damned if you can find them to do so. The Walkers rarely interact with those from outside the Rust Garden, and rarer still, in a way that doesn't involve the Walkers killing intruders into the Rust Gardens, setting out the bodies (or prisoners) so the next Razorstorm strips them down to the muscle, and then displaying them on the border of the area. If you want something they have, it's safer to just wait in one of the border towns and settlements, even though you may be waiting for a very long time. 
They few that have survived conflict with the Red Walkers report that they rarely use firearms, preferring to close into melee range with advanced stabbing and cutting implements. The firearms that they do use, seem to hold some sort of ceremonial importance to the people. Their exact nature, however, is rather unknown.