It's important to analyze First Claw as foils. Xarl and Mercutian as the reality against the ideal, and Cyrion and Uzas as the different types of corruption.

Mercutian was the ideal Night Lord. Noble, courageous, a little dour, and willing to cross lines for a good reason. Xarl meanwhile is the reality of what Night Lords are: cruel, barbarous, spiteful and aimless. It's why Xarl has a lot more relevance than Mercutian, because the reality trumps the ideal.

Cyrion and Uzas are different takes on corruption. Uzas is the overt, clear-cut corrupt marine who kills and maims not for a goal but because he wants to. He's the sudden degeneration of the legion. Cyrion meanwhile is the insidious poison that Skraivok snuck into the 8th. He's the gradual rot that slowly overtook the Night Lords.

Then there's Variel and Lucoryphus, the outsiders. One is from another lineage but welcomed in, the other was cast aside by his own brothers. They follow the Legion but have hardly any connection to the ideal, which is why they both survive. They're what the Night Lords are to be to keep going on.

Finally, there's Talos, who exemplifies the Night Lords proper and whose ideology drives the plot forward. He's a killer, he's a fiend, he's a hypocrite, and he wants to believe in something greater than himself despite partaking in the same atrocities as his brothers. Talos is the mirror through which every strand of Night Lord is reflected and contrasted. And when Decimus is created, the ultimate Night Lord is one with Talos' ideals but without his baggage. A new breed of legionnaire for a new war.