Winter Break was the first book to be split in two tomes:
From the Depths (2006).
Poison of the Past (2007) was further split in two volumes due to its sheer size, though published simultaneously.
Heart of the Beast was to be the last book in the series, but had to be split in five volumes. "Ending Fatigue" doesn't even begin to cover it.
Lies of Mirrors, Truth of Steelnote In original Russian, the title is "Truth of Steel, Lies of Mirrors" but that translation doesn't preserve the original's poetic meter. (2008).
Orb of Fates (2009).
Blue Gaze of Death was ostensibly the last tome of the last book but...
Furthermore, after Sunrise, a collection of previously published and new novellas about Eterna and Kertiana will be released in a single bound volume entitled Flame of Eterna (TBA). Said previously published novellas include:
Flame of Eterna (2004). A distant prequel to the novels, set before and around the fall of Galtara. Spoils a lot of reveals of the later books.
Taligoian Ballad (2005). A less distant prequel (published as the prologue to FWTW), set during Francis Ollar's coup to take the Taligoian crown, 400 years before the novels.
White Spruce (2006).
This series contains examples of:
Alien Non-Interference Clause: The Guardians of Sunset are forbidden to use their powers before Normal People of the worlds they protect. However, one of them (strongly implied to be Rinaldi Rakan from Flame of Eterna) finds a loophole in order to save Roque Alva from assassins: he cannot use his powers—but his swordfighting technique, honed to perfection over one and a half thousand years, is exempt. Roque is left with an impression that he was saved by the Left-Handed One (i.e. The Devil) himself.
Animal Theme Naming: Three out of four incumbent Dukes are commonly referred by their respective heraldic animals' names: Roque "The Raven" Alva, Robert "The Palfrey" Epine, and Valentine "The Squid" Pridd. Interestingly, Richard Oakdell, who should theoretically be known as "The Boar", is never referred thus.
Apparently Powerless Puppetmaster: Stanzler plays up his apparent lack of political power to pull Richard into his schemes—and Richard is pretty much the only one in the series who buys this act.
Arc Number: Four. Four noble houses (each subdivided into four clans), four creator deities, 400 year-long ages...
Arson, Murder, and Jaywalking: in vice versa order, but almost literally. Word of God says that Richard Oakdell's inevitable moral decay, which drove him to attempt of Alva's murder and killing the queen Katarina was shown from the very beginning; this soon-to-be-traitor-and-murderer tried to kill the annoying rat in Laic Academy.
Artifact Title: Possibly the entire series. "Eterna" was apparently an interdimensional fortress that served as the base of operations for the Guardians of Sunset until its destruction long before Red on Red. The Guardians of Sunset are guarding the inhabited worlds from unimaginable monstrosities from beyond but began steadily losing after Eterna fell. All of this is mentioned on four pages in an early book, tangentially referenced in the prequel novella Flame of Eterna... and never brought up again in any of the nine novels published thus far.
The Atoner: Most of Robert's actions as Proemperador of Ollaria in the later books are motivated by his realization of just how much his and Aldo's (mainly the latter, but Aldo had conveniently left the world of the living before the consequences caught up with him) ambitions screwed things up in the city and the desire to make up for it.
Stanzler. He showed all the soon-to-be Big Bad signs in first two books, but suddenly it came out that he is just a petty blackmailer, who was blackmailed too.
Big Damn Heroes: When Richard Oakdell happened to have duel with seven enemies at once, Alva arrived just in time to take six of them and equal the chances. Although he could have taken all seven, he just didn't want to deprive Oakdell from all the glory.
Big Screwed-Up Family: Pridds, Arigots, Oakdells... Rakans in the prequel, Flame of Eterna, also fit perfectly.
Honor: Characters who keep their word, stay loyal to their friends and superiors, and take care of their subordinates generally live longer and healthier lives despite having to occasionally suffer for it. On the other hand, those who behave detestably and keep backstabbing others often meet very messy ends (though almost never before causing a lot of harm).
Duty: Those who know their duties and carry them out to the end, regardless of personal cost, tend to survive hardships that kill the less determined.
Humility: Knowing their limitations keeps characters from harm and bad decisions, while believing in one's infallibility causes a lot of grief.
Political realism: It is repeatedly hammered in that governing other people is not a permission to arbitrarily shape a country according to one's own wishes but a heavy duty to facilitate societal order. Those who fail to understand that usually cause a lot of harm to everyone (including themselves).
Secular humanism: In the matters of faith, both outright moral corruption and extreme dogmatism are shown as equally harmful. A middle way, focused on knowing the human nature with both its flaws and strengths, is advocated.
Rational skepticism: Blind faith in certain ideas or individuals repeatedly causes chaos and pain, as it is easily exploited by unscrupulous schemers. Critical thinking (in conjunction with other virtues listed above) usually helps avoid manipulation.
Dracco, Robert Epine's horse, is half as cool, for it is half the same breed.
Conflict Killer: tons of them. In Face of Victory Robert Epine, who was desperately trying to lead his rebel army to not very bloody failure suddenly faces the fact that commander of government forces general Luras has decided to switch sides and embrace Aldo Rakan as his king.
In the next two volumes Robert with the same desperation tries to rescue Alva for I Owe You My Life reasons and drag Aldo Rakan along with Aldo's Grandma out of this "royal" shady enterprise. No way: Alva is to be resqued by Valentine Pridd (first time) and Marcel Valmes (second time) and Aldo - killed by Moro.
Corrupt Church: Esperathists. They are so corrupt, it took a destruction of all the Agaris City along with them to save the world from their filth.
Judging by the massacre on Octavian Night, Ollarian Church is hardly better.
Fisher King: The kings of Golden Anaxia, as well as the four Dukes, wielded very direct power over their lands. This connection extends even to their modern descendants, as seen in the destruction of Nador, directly caused by Richard's betrayal of Alva at the latter's Kangaroo Court.
Good Shepherd: Bishops Honoré and Levy. Well, bishop Bonifatius is not bad, too, and father Germane.
Gosh Dang It to Heck!: Numerous examples, most notable are "Sundered Serpent!" instead of "damn!" and "Left-Handed" instead of "devil". More humorous are Matilda's "...your cavalry!" (with an obvious implied expletive omitted at the beginning) and Valmon's "Nightingale your toad!"
Hate Plague: In Midnight, the entire city of Ollaria (save a few thousand who are somehow immune) succumbs to an uncontrolled desire to Rape, Pillage, and Burn everything in sight.
The Heretic: King Franciscus I, a.k.a. the Maragonian Bastard, who established the Ollarian Church.
Heroic Bystander: Not quite a bystander, but in Midnight, while Ollaria succumbs to the Hate Plague and Robert tries to lead the uninfected out of the city, one of said group, an innkeeper, approaches Robert to tell him that they are passing by his inn. Robert at first assumes that the man would demand from him to save his stuff, but the innkeeper instead simply gives him and his men permission to plunder his store for food—something they're very short on—to feed the others, before disappearing. This provides an important clue to Hate Plague immunity: only those with a strong sense of duty (like Robert and his loyal guards) and/or a readiness to make sacrifices for others (like the innkeeper) seem to resist it.
Hunting Accident: This is what officially happened to Valentin's older brother Justin.
I Am Spartacus: In Red on Red, several unars "confess" to being Suza Muza when Captain Aramona finds (planted) evidence against Richard. Since some of them are from privileged families, Aramona has no choice but to let them off lightly and simply lock all of them plus Richard up for a night. It turns out, however, that none of them was the real Suza Muza, who continues to prank Aramona during their incarceration.
Idiot Ball: if Richard Oakdell was a little bit smarter, plot would be finished on vol.2. Good guys in general have a firm grip on Idiot Ball, primarily by refusing to take meaningful action against their obvious enemies before the latter stab them. That's the only conceivable reason the villains, smug snakes they are, ever get anywhere.
I Know Your True Name: Names seem to play some role in Kertianan magic, for instance, when the Piebald Mare comes after Aramona's son, Alva raises him into the Kenalloan nobility, effectively giving him a new surname (Calperado)—which apparently saves his life, as the Mare doesn't bother him anymore.
In the Blood: Only males descended from Four Gods have magical powers. Even though they have no idea how how to use it anymore.
Non P.O.V. Protagonist: Alva is the essential character of the cycle, yet his actions are the only ever observed through the eyes of others. Another Duke, Valentine Pridd, likewise never gets any attention but he is also less of a world-shaker.
Powder Keg Crowd: A crowd is one of the scariest monsters found in this series—and it gets worse every time it reappears (especially since there seems to be some supernatural nasty that feeds on people going mad). In From War Till War, the Ollarian riot against Bishop Honore is stopped by the timely arrival of Alva's troops, but already in Winter Break, a stampede at Dora leaves hundreds dead and wounded. And then, in Midnight, it all culminates in the riots over trivialities across the Golden Lands' capitals, starting from Ollaria again, which are described in chilling detail.
Protagonist-Centered Morality: everything is done for the Talig's sake, is good. What's done against Talig (and it's First Marshall) is BAD. That's why Alva can drown babies and Aldo is not allowed to take hostages.
Reluctant Ruler: Alva is strongly implied to be the real heir to the Golden Anaxia but has so far dodged all attempts to put Talig's crown onto his head.
Shoot the Dog: Because of Blood Oath given by Alva to king Ferdinand, Alva cannot leave him captured and must willingly surrender to Aldo Rakan after successful runaway. And there is no way to rescue the king along with Alva. But Marcel Valmes somehow figured out that if the king dies, Alva is free from his Blood Oath. Well... poor Ferdinand.
Robert sacrificed himself to White Fox for the sake of his Birissian friends Garizha and Milzha - only to find pretty soon that these friends are already beheaded. Good thing Alva was there to spare his life.
When Alva's assassination and Born's uprising failed, Egmont Oakdell knew for sure that any attempt of riot is doomed while Alva is in command of the military. It didn't prevent him from uprising, though. Results were predictable: he was defeated and killed by Alva.
His son Richard didn't went much futher. He knew for sure that his inept efforts to kill Alva, regardless of success or failure, will lead to his own death. He would either be killed by Alva or executed for murder. But he tried. Because he completely missed the point. Good thing Alva spared him too. And then Richard tried killing him again.
Stupid Surrender: Alva had arrived to the king Ferdinand's scaffold (because king was to be executed by Aldo Rakan's orders), laid the path of Blood and Glory through enemy lines, slashed treacherous general Luras in two halves and... surrendered to Robert Epine with no attempt to save the king at all! Made even more senseless by the fact that poor Ferdinand was later murdered in prison, anyway.
Kazarone Tuhhup from the first book. Known basically by his Badass Boast to trample Alva's army into horse crap. Guess who was trampled instead?
Katarine Arigot. Richard Oakdell might have deserved some ass-kicking, but to scold one when he is on a verge of insanity and has dagger in his hand is the very bad idea.
The Tower: The mysterious wandering Sunset Tower that Richard encounters in the Varastian steppe in Red on Red. It is said to be an exact copy of the tower still standing in Galtara, one of four such towers built in the time of the Golden Anaxia and the only one to have survived. Witnessing the Sunset Tower appear is considered an ill omen by the majority but Alva seems to think otherwise.
Troll: During his Kangaroo Court, Roque keeps referring Aldo "the gentleman in white pants" (referring to Aldo's wardrobe choices that supposedly mimic the ancient Galtara fashion), driving the vainglorious usurper nigh mouth-foamingly angry.
Verbal Backpedaling: Exactly what happened in Orb of Fates when Richard had eavesdropped the little chat between Katarine and Stanzler. Poor youth couldn't stand the fact that he was totally fooled by his Love Interest. And moreover, she despises him for that. However, he happened to have dagger. Bye-bye, sweet Kat!
Zombie Apocalypse: An interesting take on this trope is found in Midnight: whatever supernatural nasty is affecting Ollaria, it brings out the worst in most people, exacerbating their petty vices to the point where the are little more than mindless clumps of hate and destruction. Only a few thousand citizens are not affected and their only salvation is to kill the infected to fight their way out. But the Hate Plague is also highly contagious, allowing it to spread beyond the city and continue to threaten the survivors. Interestingly, immunity to the infection is conferred by inner virtues (primarily honesty and readiness for self-sacrifice)—which also, however, tend to accelerate the infection in others, as Selene Aramona's case shows. Parallels may be found between the description of the Ollarian riots and historical Real Life riots seen from the law-enforcement's POV.