I try to let plot, world and characters develop as organically as possible. One major upshot of this is that bit-part players, conjured into existence to fill a momentary need of the narrative, can take on a life of their own. If a niche arises for them, they can take on real lives of their own. Here are a few of my favourites who have elbowed their way into the story and earned their way into the big league. Big warning: moderate spoilers throughout — nothing that's a plot-killer, but still. I'll specifically try not to spoil any part of War Master's Gate.
Helmess Broiler and Jodry Drillen
I wrote about the way these two pushy Collegiate statesmen crowbarred their way into the narrative here. Suffice to say they went from a cameo and a mention in The Scarab Path to redacted minor characters in Empire and in Salute the Dark respectively, to major players by War Master’s Gate. Bloody politicians.
The first Imperial embassy to Collegium includes a Beetle diplomat named Honory Bellowern, and we see very little of him, save that he appears a bit green and gets on the wrong side of Thalric at one point. He turns up again on the diplomatic staff, in the Sea Watch and then is in and out of the narrative for the duration, so that someone who is just a name and a function essentially pieces together their own story of ambition in the Imperial hierarchy just from the brief moments when we see him. Later we meet presumably a relative, Founder Bellowern, an enterprising Consortium magnate, in Blood of the Mantis, a collector of rare curios. At that point, with the surname belonging to multiple characters, the family took on a life of its own, and in Seal of the Worm we even meet the aged patriarch, and get some idea of just how much clout the Bellowerns have. Their series function becomes an example of just how powerful non-Wasps can be in the Empire.
Balkus and Sperra
A couple of Scuto's footsoldiers from Empire, Balkus the nailbowman and Sperra the artificer/medic survived the fight at the railyards memorably enough that, when Stenwold needed some extra pairs of hands in Dragonfly they were the obvious choice. From there, they quickly graduated from spear-carriers to major characters. Balkus, the Wedge Antilles of the series, led the defence of Collegium against Vek and was the Collegiate PoV character in the major battle of Salute the Dark. Sperra drew the short straw and got herself tortured by the Sarnesh. In War Master's Gate they appear as the representatives of the new city of Princep Salma.
Te Berro is perhaps the best example of a minor player who somehow fits a complete personal plot arc in the background of the main plot. He starts life as a Fly-kinden Rekef officer backing up Thalric in Empire under the auspices of General Reiner. Later on he has defected to General Maxin's rising star, for whom (and for the Emperor and Uctebri) he engages Scylla, Gaved and others (and I'm not doing him here, but Gaved is another character just like this) to steal the Box of Shadows. When that goes south, he presumably incurs considerable disfavour, because by Scarab Path he is living incognito in an Imperial records office, where Thalric tracks him down. In exchange for his help, Thalric arranges for him to get transferred to sunnier climes, but Thalric's help is very seldom good for people. In the Air War te Berro meets a tragic end whilst trying, of all things, to mend his ways. There is actually an entire complex book's worth of plot attached to poor te Berro. A large chunk of the series could be written entirely from his point of view.
In Air War there is a very minor character who nonetheless gets a memorable introduction. Castre Gorenn is a Dragonfly archer who refused to stop fighting the Twelve Year War — which amongst other things implies she is a traitor who is disobeying her Monarch. She turned up at Collegium's gates declaring herself to be the Commonweal Retaliatory Army and is blithely ignorant about almost everything to do with her newly adopted people. At first she's there for colour — for the same reason there are so many different nationalities in Casablanca, to show that the society under threat is diverse and inclusive, as opposed to the monocultural invaders (1). With that colourful start, however, Gorenn came to assume a very different function. As the situation deteriorates, as peace collapses and the war becomes desperate and savage, Gorenn shines. Her Inapt world of valour, recklessness and passion is far more suited to the chaos that war brings than is the ordered Apt world of the Collegiates.
Ah yes, Allanbridge the aviator, who turns up first (I think!) in Blood of the Mantis to ferry the heroes to Jerez, and has been ferrying ever since. A friend of Stenwold's, and someone who obviously trades in more than the merely legitimate, he's no Han Solo, but a businessman who wants no trouble. Instead of which he gets called on constantly and unfairly to carry people about to increasingly distant destinations. And he gets more complicated as he rubs shoulders with the protagonists, until by Sea Watch he is keeping dangerous secrets from Stenwold, and by War Master's Gate… but I said I wouldn't spoil any of that.
Sartaea te Mosca is introduced in the Air War basically to be the advisor, support and friend-in-a-high-place for Eujen, the Antspider and the rest. A Fly-kinden magician of very little power, she teaches magic to Beetles who don't understand it (having taken over the post from Doctor Nicrephos, who has his own little plot in Empire and Dragonfly). Her role persists into War Master's Gate, and she is one of the 'normal' Collegiates used as a touchstone for the effects of the war on the city. That's about all I can say for now, save that in Seal of the Worm she has a far more important, and hard-edged, job to do, enough to warrant her getting on this list. As an additional piece of trivia, there are a number of characters in the series that are very loosely inspired by friends of mine, and te Mosca is a fond nod to my friend and fellow author Frances Hardinge. So now you know.
Varsec is practically the patron saint of this list. We don't actually know his name until Heirs of the Blade but he's kind of retconned into the continuity when he's introduced as the man behind the Imperial invasion of Solarno in Blood of the Mantis two books earlier. That invasion, characterised by daring air support and the use of Wasp mindlinking for communication, sets up Varsec as a maverick, and we meet him under the shadow of the axe. However, his plans for a new air force lead to the events of the Air War, and he is one of the few Imperial artificers who appears to be able to match Drephos idea for idea. His rocky career continues throughout the series, another little plot arc you can piece together.
And General Tynan, commander of the Second Army, known as the Gears, because it just grinds on no matter what. Tynan was never meant to be a major character. He turned up towards the end of Salute the Dark when he brought an army to the gates of Collegium. He captured Stenwold Maker, and had the chance to do away with the Empire's greatest enemy. But he didn't. And in that one scene he has with Stenwold and Arianna, it turned out there was a real connection between Collegium's War Master and the general of the Gears. Tynan just sprang into being as a far more interesting and detailed character than the role probably merited, and although we hear nothing about him for several books, he was always in the back of my mind as a returnee. So it is that we find him working his farm in The Air War like a retired Roman when the call to arms comes in: the Second is marching again. And from that point, he's a sufficiently major protagonist that he gets his own character bio at the start of War Master's Gate.
(1) I am always rather depressed by settings where a monoculture — frequently militaristic to the point of fascism, is shown as the valiant defenders against a vastly diverse enemy. 300, Halo and Space Marines of all stripes, I'm looking at you.