I haven't gotten into much detail about the barbarians at the fringes of Galactic Christendom, but they will be a significant presence when I get around to "The Taking of Countess Gabriella Robin". As with the Periphery and beyond in BattleTech, they too are--generally speaking--using technology comparable to the norms of Galactic Christendom. They also are often in thrall to one or another of the Nephalim or the Fallen Angels, usually as the literal progeny of said master or otherwise corrupt in a fundamental way that renders them a subject people- and then their culture finishing the job of yoking them to the master's will.
As such, when they show up it's a big deal. The deeper into Civilization they penetrate, the bigger the threat they present, and the opening of the aforementioned story is one such barbarian raid on a world commonly believed to be beyond the reach of the barbarians. How this happened, and why, is a subplot for the supporting characters to handle while Our Hero chases after Our Damsel to rescue her from being forcibly bound to the barbarian warlord that seized her.
So, later this year, get ready to see our Paladin of the Solar Guard fight his way through a barbarian horde to rescue the beauty of the galaxy from a barbarian warlord set on possessing her- and he alone.