The Ctarl-Ctarl Empire are not a huge empire, about 36 worlds at this point. but they're not alone. they have friends.
enter The Caliban League>
my inspiration came from, not from Shakespeare, but from Warhammer, but aren't as much of a straight lift as this might imply. Caliban itself is forest from pole to pole.
The Caliban League consists of 85 star systems, but those systems are incredibly wealthy in resources. This is why the Ctarl-Ctarl and the Calibanites could afford to build a gate from scratch.
The knight houses of Caliban are some of the few people who could fight a Ctarl-Ctarl to a standstill in melee combat.
The gate within the Ctarl-Ctarl empire is an original gate, and remained in quite good shape. It's original destination gate was completely destroyed. The construction a new destination gate within the Caliban League was a joint effort between the Ctarl-Ctarl empire and the Caliban League.
The knight houses are very selective of who they recruit, but not from where they recruit. Knights often are expected to pick their proteges from the poor and the humble in order to raise them up. The knightly houses, more akin to orders than a hereditary house, suffer few fools or glory seekers.
What is the washout process like for recruits who don't make it? Here's the thing, someone who gets far enough to be selected and begin training but washes out isn't doomed. They likely are still very worthy soldiers, the path to the knights oath is very demanding, not everyone can make it 100%. This speaks to no failing to the proteges, but simply that the order cannot yield to mere 90% adherence. Oftentimes these washouts become quite skilled warriors and commanders and statesmen in their own right.
What does the knight's oath actually demand that makes it the final threshold so many can't cross? The oath demands that so long as the knight shall breath, their existence is to protect the league and all who dwell within, to put the good of the league and the knight houses before their own desires, to reject the desires of pride or ego for the rest of their days, and to be ready to lay down their lives in glory or obscurity.
this is why there is such a high washout rate.
What happens when a knight breaks their oath?
See, there is a number of mechanisms in place to prevent that. A knight feeling a pull in those directions should seek counsel of their brothers and sisters (knighthood makes no requirement of gender).
That's said, a Knight falling to such temptation is not impossible, and these fallen knights are incredibly dangerous individuals.
That said, any knight who lives long enough will eventually lay down their blade, usually in old age, and take the role of an oath watcher. Those who have served long to the point they can no longer carry the duty that comes with the mechanized auto-plate armor.
There is no shame in recognizing when one has reached the end of physically carrying out the duty of the knight, and are still bound to the oath, leaning more heavily on the monk side of warrior-monks.
the ones who pursue the fallen knights are known as the order of the black tapestry, also known as blackhoods. they are drawn from all the knight houses, they do not speak highly of their deeds, there is no real joy in this. they don't go after knights who have merely stumbled, they go after ones that have gone full tilt betrayal.
What does the mechanized auto-plate armor actually look like and how does it function in combat?
Aesthetically, it's a lot closer to fallout power armor than the armor of an astartes.
Common gear tends to include a kinetic dampener shield, some form of electro-blade sword, though the style will shift from house to house, some form of heavy laz-rifle, and those are the most common load outs. Again, it'll vary on specific knightly houses on what a knight tends to carry specifically.
The average knight is a lot more jovial outside of combat than one would expect. They are sons and daughters of this league, like those they protect. They do not keep themselves locked away form it.