Air Vent Passageway: Variation - they're not quite air ducts, but Attolia's palace is run with hypocausts, a series of small tunnels built to funnel smoke to provide heat in the winter, but Eugenides has better uses for them. To keep up the modern air duct parallel, it's outright mentioned that the only reason he can fit into them is because he's so small.
Balance of Power: Eddis maintains the balance of power between Sounis and Attolia by acting as a barrier between the two against invasion. Of course, that means either country (particularly Sounis) would like to get control of the other, and Eddis is in the way...
Brought Down to Normal: Subverted. After getting his hand cut off early in the second book, Eugenides sinks into a deep depression, believing he's now useless (because what can be stolen with only one hand)? He's not.
Bunny-Ears Lawyer: The king of Attolia is petulant, whiny, slumps in his throne like a printer's apprentice, dresses in colors that would suit a canary, and generally behaves without an ounce of royal dignity. Don't let that fool you.
In the third book, Eugenides uses a call back to the prayers Attolia heard him making when she had him imprisoned to keep her from executing her captain of the guard for failing in his duties—at protecting Eugenides.
Changing of the Guard: While Eugenides is a highly prominent character in each book and his character has by no means completed its development, the spotlight shifts to the queen of Attolia in the second book, Costis Ormentiedes of the Attolian Queen's Guard in the third book, and Sophos, the heir of Sounis, in the fourth.
The Chessmaster: Eugenides most notably, though the Queen of Attolia, the Queen of Eddis, the Magus of Sounis (the king's advisor) and the Mede ambassador Nahuseresh all have shades of this. Some are more successful than others.
The Chew Toy: Costis, thy pain and humiliation are an unceasing source of amusement to thy fans.
Cuffs Off Rub Wrists: Averted with Gen at the very beginning of the series. Several months of jailtime does not do your wrists any favors.
The condition of his wrists is made rather worse that at the beginning of his sentence, he would regularly slip the cuffs off and have to jam them back on every time a guard came by.
On their first stop, Pol, the guy who basically amounts to Gen's parole officer, has a look at his wrists. One of them just needs time and maybe a little salve to heal; the other has little pockets of infection deep enough that Pol needs to lance them with his knife.
The queen of Eddis is a bit prone to this, too. As is Eugenides, especially in the first book.
Defrosting Ice Queen: A big part of the main plot of The Queen of Attolia, and shows up quite a bit in King, too.
Diplomatic Impunity: Let a Mede ambassador into your country at your own risk. He'll try to bribe your nobles, sneak soldiers into your country, and make you his puppet, all while being very polite to your face. And you can't do anything because making a bad move against an ambassador is an act of war.
Subverted in A Conspiracy of Kingsby Sophos.
"You shot the ambassador?”
"You gave me the gun."
The Disease That Shall Not Be Named: The reclusive Mede emperor suffers from something called "tethys lesions." Fans speculate it's a fictional name for syphilis. Alternately, leprosy.
Dumb Is Good: Most of the characters, good and bad, are very, very smart. However, there is one notable exception. In the fourth book, Sophos is saved by the Big Bad's idiot daughter, Berrone. She helps Sophos escape from his kidnappers and hides him as a slave. She didn't even recognize him, she just couldn't bear to see anyone that badly treated. Berrone is a total sweetheart and a well-known soft touch, which means that everyone likes her and everyone takes advantage of her.
Ear Worm (an in-universe example): "The King's Wedding Night," apparently. Even dog-loyal, humorless Costis finds himself absently humming the tune.
Establishing Character Moment: In-story example with Attolia. We the readers already know the queen, but for her barons, her claiming the throne definitely led them to figure out this was no puppet queen they were dealing with.
Everyone Calls Him : Several examples. Eugenides is the name of the god of thieves, and many of the Thieves of Eddis are named after him. Thus it's both a name and a title. In addition, all of the royalty in the three countries take state names derived from the name of their countries (Eddis Helen, Attolia Irene, Attolis Eugenides... Sounis's real name is never mentioned, but in the next book it's like to be Sounis Sophos. If Sounis ever got his way and married Eddis, she would be Sounia.)
Expository Hairstyle Change: Gen's hair is long enough to braid in The Thief, but gets cut early in The Queen of Attolia and remains short thereafter.
Guns turn out to be extremely important to the endgame in A Conspiracy of Kings.
Fantasy Pantheon: And a very active one, at that. Comes, of course, with such curses as, "Gods damn, gods damn!”
But they’re extremely careful which gods they swear by (at least in Eddis, where the population seems generally to be made up of more true believers and fewer skeptics as compared with Attolia and Sounis).
Finders Rulers: Hamiathes’ Gift, which gives its possessor claim to the throne of Eddis.
First Episode Spoiler: The end of The Thief reveals that Eugenides is the Thief of Eddis, in service to the Queen of Eddis, and part of the Eddisian royal family and has been screwing with EVERYONE (and does it on a regular basis). There are three books that follow. Try explaining to a friend why they should read this series without somehow spoiling them. You can't.
In addition, do not buy The Queen of Attolia and The King of Attolia at the same time; not only does the back cover spoil the fact that Euginides becomes king of Attolia (which can be guessed by the Genre Savvy reader), but it also mentions that he is in love with the queen, who had absolutely zero redeeming qualities in the first book.
First-Person Smartass: As if The Thief could be described any other way, when it's narrated from Gen's point of view?
Foreshadowing: The books are full of it, as a reread after knowing the Twist Ending shows. For instance, in the first chapter we have "He wanted to know my name. I said, "Gen." He wasn't interested in the rest."
"She may be a fiend from hell to make me feel this way."
Probably most notably, Gen's entire conversation with the Magus before he steals peace.
Gambit Pileup since he's hardly the only one trying. The trope is so prevalent throughout the series, and the plans so complicated, that is possible to read the books multiple times and make new discoveries of mini "Gambits" acts that seemed innocuous every time you read.
Gambit Roulette: There are many plans, many planners, and all of them complicated.
Gentleman Thief: Eugenides, to some extent. He's petulant and whiny, but he's also very regal.
God Save Us from the Queen: Played with, though the queen of Attolia, who despite a very unpleasant reputation, is a competent ruler and she has a Freudian Excuse for some of her behavior. Not to mention that her barons wait like a pack of hounds for the day she slips up. So in fact she's doing whatever needs to be done for the good of her country, which is no easy task in a sexist government.
Government Procedural: Among the main characters, we have the sovereigns of three different nations, the brother to the heir of a fourth, and a number of advisors to said rulers.
Graceful Loser: Sejanus loses with style and honor. (If only because his brother’s life is threatened if he does otherwise.)
Guile Hero: Eugenides. Basically everything he ever does shows how terrifyingly brilliant and cunning he is.
Also, Attolia and the Magus. Eddis, Gen's father, and even Sophos have their moments.
Gilded Cage: Eugenides captures the Magus in the second book and has him housed in a pleasant lodge in the country, where he he is cared for/guarded by Eddisian soldiers.
Gunboat Diplomacy: The fabulous unified rout of the Medes by the combined Attolian and Eddisian forces at the end of The Queen of Attolia.
Hairy Hammerspace: One of the reasons Gen likes his hair long. And what enables most of the climactic plot twists of The Thief.
Handicapped Badass: Eugenides after the opening chapters of The Queen of Attolia, depending on how you look at it. It’s clear that early on, Attolia and even Gen himself consider the loss of his hand a crippling handicap (“What can a thief steal with only one hand?”), but if anything, it ultimately helps him on the road to becoming much more awesome than anyone (except maybe Eddis) would have expected.
[Attolia] wondered when she had sunk so low that she had begun torturing boys.
Heroic Bastard: Played with in the first book, Gen lampshades and disputes the trope, telling his noble companions that although they might assume otherwise, his parents were married, and his sisters have also made respectable marriages. Since it's later revealed that he's not actually lower class, it's not quite a subversion of the trope.
‘My sisters are even married, and honest housewives to boot!' At least they were mostly honest.
Hypocritical Heartwarming: Eugenides doesn't have a good relationship with his cousins, but after his maiming in the second book, they all jump at the call to lead Eddisian reprisals (including those who were the worst bullies to him), and several of them die heroically in combat.
I Did What I Had to Do: Attolia's cruelties were all to keep her country stable and in the hands of someone who wanted the country to prosper.
Impossible Thief: Among the things Eugenides steals: peace, a queen, and three entire countries.
In Spite of a Nail: Despite the very different path of history, the books seem to be set around 1500 and a lot of technology from that period or even later are present: printed books, wristwatches, guns, stained glass windows, etc. There's also a mention of a plague a few decades previously, which might be similar in setting to the Black Death.
Ironic Echo: "Diplomacy, in my emperor's name." Later followed by, "Diplomacy, in my own name."
And Eugenides himself, for that matter. Famous in three countries for being a Consummate Liar, a chronic snarker who always has something acidic to say, and a constant complainer, but really a good guy underneath.
Jumped at the Call: Gen. It's his dreams of greatness that set the whole first book rolling.
Karma Houdini: Nahuseresh stirs up an ugly three-way war, buys Attolia's barons against her, kills the barons he can't corrupt, incites Attolia into cutting off Gen's hand, and does pretty much everything he can to take Attolia's country from her. And then gets away scot free in the end.
Kick the Dog: Attolia cutting off Gen's hand, although the ramifications the act has on her conscience deconstruct the trope and make her more sympathetic. Played completely straight with Nahuseresh, though, who is a giant bastard.
Kids Are Cruel: Gen's cousins held his head in a water cache and wouldn't let him out until he agreed to spit insults about his family.
The Kingdom: Three kingdoms: Attolia, Eddis, and Sounis.
Pretty much the entire Eddisian court counts on some level. They're all related in some capacity, so there are priests whose entire duty consists of sorting out family trees to figure out who can marry who.
Viciously deconstructed, as well. Gen may have been entranced with Attolia when he first met/saw her, but he didn't really love her until he got to know her(and not "Attolia") whether it's through information obtained from the magus or just out-and-out spying on her.
Calf love doesn't usually survive amputation, your majesty.
Low Fantasy: Although it's in the Sci Fi Ghetto in terms of where it's shelved in libraries and bookstores, there's really no fantasy at all besides the fact it's set in a different universe. And the highly active pantheon.
MacGuffin: Hamiathes's Gift in the first book. Only then it saved Gen's life, so...
Made a Slave: Sophos in A Conspiracy of Kings. Unusually, he describes himself as much happier in the simple life as a slave than he had been before.
Martial Pacifist: Eugenides is somewhere between this and a Technical Pacifist. He hates the idea of killing and doesn't really even like physical combat, and often finds himself in the position of The So-Called Coward, but is a very skilled fighter, and will kill when absolutely necessary.
The Masochism Tango: Gen loves the extremely ruthless Queen of Attolia even after she has his hand chopped off
Narrative Profanity Filter: Used in the books to filter out the harsher language (although some swearing is left uncensored). One line from A Conspiracy of Kingsjustifies the use of the trope by adding in characterization of the main narrator:
I screamed at them every curse I ever practiced when I was alone, trying to imitate the Thief of Eddis, but I doubt I sounded anything but hysterical.
No Hero to His Valet: While no one who knows him doubts he's one of the most capable people in the universe, Eugenides' cousins, father, wife, gods, and even his Lawful Stupidbodyguard all put up with his royal petulance only for so long before threatening to sit on him.
The Not Secret: The first Tomato Surprise at the end of the first book turns out to be a surprise only to Sophos, and the readers, much to Gen’s disappointment. The magus, Pol, and Attolia at the least had all figured it out beforehand.
Oh My Gods!: Characters frequently swear by an assortment of gods, with or without specific names. And then sometimes they just invoke their patron god, leading to conversations like this:
Costis: Oh, my god.
Gen: O my god. You want to call on the god appropriate to the occasion. After all, your god would probably be Miras, light and arrows and all that sort of thing, whereas my god is a god of balance and, of course, preservation of Thieves...
One Degree of Separation: Everyone in Eddis is apparently related to everybody else. It's so egregious that they have special priests whose job it is to track the genealogies and figure out who can marry whom. Truth in Television for a small mountain country, of course.
Opinion Myopia: Some of the reactions of fans online to people who don't like the books in general or the main romance in particular.
Pals With Jesus: Eugenides is noted for not only talking to his gods, but for having them talk back.
Sometimes for minor things, too: “Stop whining and go to bed."
Sophos gets this treatment in The Thief, too, though it’s more Reluctant Heir since his uncle is still the reigning king. Sophos would much rather live out a leisurely scholar’s life with the magus than inherit Sounis.
Reluctant Warrior: Eugenides, who hates to kill people. Despite being quite good at it.
Royals Who Actually Do Something: Every monarch in the books is completely competent at managing his or her kingdom and much of the Eddisian royal family is engaged in government/military work in some way.
Shout Out: To Rosemary Sutcliff and Diana Wynne Jones in the first book. And DWJ again in the fourth.
The Spymaster: Relius, officially. Though several characters fit this trope despite not acting in any official capacity. There are characters who fit this trope even though it's literally their job to have other people do it for them.
One of the central conflicts of A Conspiracy of Kings.
Theme Naming: Amusingly subverted for irony: the beautiful, ruthless queen of Attolia is named Irene (meaning peace), while the kind, mannish, and ugly (or at least unattractive) queen of Eddis is named Helen (after "the woman who launched a thousand ships”). Both queens lampshade this in the second book.
But Helen is as beloved by her people as much as any queen, no matter how beautiful, can wish for. If Eddis had any ships they would gladly be launched for her.
Tomato Surprise: Once in The Thief, once in The Queen of Attolia, and if you hadn't read the other books before The King of Attolia, there's one then, too.
Unexpected Successor: The princess Irene was a minor member of the royal household until her brother unexpectedly died falling from his horse. A year later her father followed and she was crowned queen of Attolia.
Also, the princess Helen. Having two older brothers and one younger one, she wasn't likely to inherit until all of three of them died of plague. When her father died months later, she became the crowned queen of Eddis.
Unreliable Narrator: Gen pretty much never says anything untrue in The Thief, but still manages to give other characters and the reader a completely false impression of himself. As a case in point, he defends the respectability of his family, noting that his father was a professional soldier and his sisters made good marriages …however, he doesn't mention that his father is Eddis’ Minister of War and his sisters are princesses. Just a small detail. Despite the later books being third-person, they're still unreliable. Hmm, mysterious narrator, no need to mention how Gen really feels about Attolia, is there? Even though it drastically changes how all of it looks?