Another idea: The Red Raven has pledged to protect planets in a certain area of space, but in turn, these planets' governments must pledge to provide the Chapter resources (including human resources, i.e., potential recruits, serfs, and servitors). These planets thus have annual festivals in which its youths must brave the "Wild Hunt" by running across the "Bone Fields" (paved with the bones of those who died); those who survive, will feast upon a portion of the foodstuffs, and be rewarded with a portion of the iron (considered a precious metal, in antiquity), gathered for the "Einherjar" (Red Raven officers, come to retrieve the resources promised them). The festivals were meant to force potential recruits to prove themselves before Red Ravens watching from orbit, and allow these potential recruits to be taken with minimal fuss.
I like the Festival idea, I've already come up with a Planetary Star cluster with some habitable worlds that they recruit from. A hive world with offworld mining concerns, a forge world which would contribute to the spread of stories, as well as a techmarine recruits, and a fortress world that trains children from the age of six to be superb soldiers, three agri-worlds that support the cluster (and provide a source of excellent scouts, trackers, and hunters, of some sophistication), as well as four resource rich feral worlds which are the source of the folklore and excellent warriors. Having a common cultural thread in the form of a festival, is a cool idea. But rather than being in honor of the Wild Hunt, it is a festival to ward them off. The Worlds using it to "cull" the undesirables (orphans, the sick, and the disruptive, ironically the ones that the Red Ravens Actually want) and appease the Hunt, so they won't come to collect others. The Red Ravens don't care if the "aspirants" are capable of making it through the impossible trials, what they are looking for is the desire to perservere. Orphans are given a family, the sick are cured, and the wild ones are given purpose, it's the will to live that will get them chosen. I'd rather Call the festival the "Hunter's Rite" or something, rather than stray from being faithful to my source material.
I'm not turning the Wild Hunt into a thing that people do. That's not what the Wild Hunt is in folklore, that's not what the inspiration is, and it's not something I'm going to change. The Wild Hunt is a Hunting Party, made up of the spirits of hunters and warriors chasing their prey for eternity. For the Red Ravens that ever elusive prey is the Forces of Chaos. They will ruthlessly hunt chaos wherever they sniff it out and pursue it until it is destroyed. They'll also hunt genestealer cults, and the biggest reason is because of the hunter's instinct bred into the bulk of their recruits from t he feral worlds of their home cluster.
I've already decided that the Einherjar reference is the First company. For those in the First Company all succumbed to the Sable Brand and "died" only to be reborn anew into the first company. It's a rite of Passage into the First Company. Many Astartes will never be part of the Honored First, but those who suffer the ash blindness and come through it, will.
As the Red Ravens wouldn't be present for every single Wild Hunt of every single year on every single planet, the planetary governors may forget for whom these resources were collected, get greedy, seize the iron for themselves (likely to be sold in exchange for jewelry) and devour the food in grand feasts meant to honor the governors themselves- and then be PAINFULLY reminded of their places when the Red Ravens reappear after many years' absence, demanding the resources promised them.
The way I see things happening are that the battle companies form task groups and are sent "a viking". The Chapter treats the task groups as raiding parties, and it's a way for them to blood new recruits. Their fortress monastery meanders through the void in the cluster, but there is always a battle company task group in garrison at the fortress, along with the bulk of the reserve companies.
I like the idea that the Governors might get greedy, and decide to divert resources allocated for the chapter for their own profit and gain. Or they become heavy handed tyrants, and need to be reminded that they serve at the Emperor's pleasure. The legends of the "Wild Hunt" are often used as an idle threat to keep people in line (kind of like the legends of "Svarte Pete" or Krampus, are used to scare children into behavior lest they be devoured). Or sometimes the Red Ravens will be evoked in the form of ancient curses, usually in the form of graffiti "Þit skyli hjarta rafnar slíta" (may ravens tear your heart asunder) to which the Red Ravens seem to have an alarming tendency to respond. Usually in a graphic manner, by splitting the offending official open at the spine and pulling the lungs out in the shape of wings, and left to be in full view of the public as a reminder of what happens when you deny the Raven's due.
The planetary governors would likely have asked the Inquisition to "save [the governors'] worlds from the Renegade Marines' predations." But the Inquisitors who did their jobs, would be shown the ancient treaties signed between the Chapter and the governors' predecessors- possibly after the Red Ravens forcibly boarded the Inquisitors' ships- forced to acknowledge the Marines' actions were legal, and back off. Those who refuse, would disappear without a trace (the Red Ravens ships' onboard manufactories would scrap the Inquisitors' ships, melt down all evidence of their existence, and recycle the materials).
I really like that idea. Even in a localized region, it could be a century or more between contacts especially if the Chapter's attentions were focused elsewhere.