A scientist named Isaac Dan Der Grimnebulin is commissioned by the wingless garuda, Yagharek, to find a way to enable him to fly again. In Isaac's search for an solution, he unwittingly releases a monster in the city of New Crobuzon.
A former girlfriend of Isaac, Bellis Coldwine, flees Bas-Lag by ship shortly after the events of Perdido Street Station. Not long after departure, Bellis' ship is captured by the forces of the pirate nation known as Armada. Most of the novel deals with events surrounding Armada's journey to an unstable and dangerous region of the seas known as "the Scar".
Twenty years after the events of Perdido Street Station, renegade railway workers, collectively known as the Iron Council, threaten the iron-fisted government control over the city-state of New Crobuzon. New Crobuzon is currently in a state of war with the rival city, Tesh, and events in New Crobuzon suggest that a large-scale revolt is on the verge of breaking loose.
The Bas-Lag Cycle series contains examples of:
Abnormal Ammo: The cactus-people (known as the cactacae) can be punctured by bullets, crossbow bolts, arrows and the like, but their complete lack of internal organs makes such weapons next-to-useless. They're also enormous, extremely strong, and covered with spines, which makes close-range weapons like blades or clubs viable, but an extremely risky and inadvisable option for most people. A sort of crossbow called a rivebow was invented to get around this problem. It fires huge whirling chakris that can sever the heads and limbs of humans and cactacae alike, but the rivebow itself is so heavy and unwieldy that usually only other cactacae carry them.
Alternative Calendar: The people in Bas-Lag use rather bold-faced names for the days, such as Skullday, Chainday, and Fishday, and this is only for the city of New Crobuzon; in the floating city Armada, they have completely different names for months and days of the week.
Perdido Street Station ends with the trade union movement crushed, the city's largest subversive newspaper shut down, and the surviving protagonists miserable and fleeing for their lives from both the Orwellian government and a ruthless crime boss.
The Scar ends with Armada's corruption exposed, but with no possible way to clean it up. The city was almost destroyed by both a civil and regular war, and the protagonist is beaten and cowed. The grand orchestrator of all this strife is free and still in a position of power over Armada.
Iron Council ends with a major uprising brutally put down, a violent revolutionary realising that he'd achieved nothing by killing the Mayor, and the largest and most hope-inspiring rebel group in the land being frozen in time.
Khepri females are red-skinned women, human in appearance apart from having giant scarabs for heads. The rarely-seen males do exist, but are literally just large non-sapient scarab beetles that exist mainly to procreate.
Anophelii are anthropomorphic mosquitoes who consist of brilliant, scholarly men who subsist on plant juices and monstrous women with uncontrollable bloodlust.
Bizarrchitecture: Armada, from The Scar, is an entire metropolis built atop lashed-together sea vessels of all sizes and designs.
Bio Punk: The Remade: bio-thaumaturges can warp flesh, bone and biology to heal, remake a being as something new, or (far, far more often) to punish.
The Khepri are an insect-like race with small non-sentient males and females that resemble red-skinned human women with a similar type of insect forming their heads.
There is also a race of mosquito people, the Anophelii, whose women are vampiric winged creatures that have fang-like protuberances that extend from their mouths to penetrate their victims. The extremely passive males have mouths that are described as being like anuses. Which is actually the gist of how mosquitoes work.
One of the protagonists in Perdido Street Station is a veteran of New Crobuzon's not-exactly-legal underground arena circuit.
A very literal example with the ritual fights of the scabmettlers. They drink a special herbal concoction, dip knives into the liquid and begin to cut themselves in intricate patterns. The unique physiology of scabmettlers makes the blood congeal quickly (but not immediately, as it would without the herbs) into a form of elaborate armour to enhance each individual scabmettler's style of fighting.
Bloody Murder: The scabmettlers of are a race whose blood clots extremely quickly. Before going into battle, they cut themselves in certain ritualistic pattern, and the results blood flows harden into armor and weapons. Blessed with Suck to some extent, since they need to medicate themselves constantly or risk spontaneous clots that will turn them into statues.
The Weavers don't have a sense of morality as we would understand it, but rather a sense of beauty. That which is aesthetically pleasing or poetically appropriate is "good" whereas that which is ugly or discordant is "bad". It doesn't help that their aesthetic sense is very different from that of humans—they seem to see the universe as a tangle of lines connecting plot points, with every object in the universe as a thread in some huge tapestry. So they adjust the threads to make it look neater, and in doing so remove the left ear of everyone within a hundred yards.
The Garuda would also count to an extent. Their society values personal freedom and individuality above all else and has only one law: You must respect others' right to choose. Those who break this law are all guilty of choice-theft. While most human crime can be seen as theft of a choice (the choice of owning an item, the choice of continuing to live unharmed, etc), the converse does not hold, meaning that people who would be considered highly dangerous criminals in human society are be put on an equal footing with people who wouldn't be seen as criminals at all to humans. And some human crimes don't fit at all: to the Garuda, selling drugs would probably be legal and moral, while preventing the selling of drugs would be heinous.
More alien are the feelings of one Garuda as she talks about being raped... she seems to bear no more ill-will to the rapist, so long as his punishment continues, and becomes quite irritated when a human considers her a victim worthy of pity; she refuses to be anthropomorphised.
Bury Your Gays: Oddly averted. In books where being a named character and being sympathetic/a decent human being is usually a recipe for death, and the named-protagonist body count runs into the double digits, Cutter of Iron Council and Derkhan of Perdido Street Station manages to make it out mostly in one piece. Key word here being mostly.
Circular Saw Good: Secret police and Cacticae security in Perdido Street Station carry Rivebows, a large crossbow which shoots spinning chakris (basically circular saw blades). In universe, the main way to defeat Cacticae (humanoid cacti) is through severing limbs.
A character also mentions that the Ambassador from Tesh is a vagabond by custom, and in the last book this is important as the villain and source of impending arcane doom is Spiral Jacobs, the vagabond.
Continuity Nod: Bellis Coldwine is mentioned in Iron Council as Isaac's girlfriend, after being the protagonist of The Scar.
Bellis is described briefly in Perdido Street Station as Isaac's lover before Lin, a brilliant linguist who had grown bored with Isaac's "rambunctiousness" and broken his heart.
The Plague of Nightmares is also mentioned in both Iron Council and The Scar.
Ulliam in Iron Council is Remade with his head facing backwards and mentions looking after dangerous animals in his previous occupation
Some of the revolutionaries in Iron Council use "Flexible" as a title for their groups and performances, in honor of Benjamin Flex, editor of Runagate Rampant who's arrested and executed in the first book.
Cool Train: The Perpetual Train, later home of the titular council which was initially crawling along laying its own rails as the forefront of an expanding railway network — it has carriages containing everything needed to keep the community of workers building the lines alive and well fed, from an abattoir to a church. It later goes rogue, and the Council organise its rails to be taken up behind it as they are laid ahead of it, so it essentially becomes a giant, moving La Résistance town.
Death World: Bas-Lag is pretty inhospitable on the whole, but it also contains at least two kinds of its own Death Worlds. The first kind have high levels of a cancerous force known as Torque, while the second is a huge wound in the world where eldritch beings crossed over from another plane.
The largest natural Torque-affected area is known as the Cacotopic Stain where getting eaten by giant caterpillar men is the least of your worries. Death itself probably isn't very high up on the list of bad things that can happen to you. Just to make this clear- a large number of people are collectively turned into a giant amoeba, just by coming near to the Stain.
There is also a man-made Torqued area which was once the city of Suroch. During a war the city of New Crobuzon dropped a Torque Bomb on it, and the result was so horrifying that they proceeded to drop even more of a different kind of Fantastic Nuke known as Colourbombs on the city... in order to cover up the damage. There are things there described as "herds of what might have once been human", and mothers threaten to send unruly children to Suroch, "where the monsters are".
The Cacotopic Stain, however, is not the worst place on Bas Lag. The worst place is the Fractured Lands, which has giant, nigh invincible, soul sucking moths halfway down the food chain. Flora and fauna there spent generations in the presence of a kind of probability magic, which caused them to evolve into highly bizarre, improbable and terrifying forms. Oh yeah, and there's a hole in the sea that monstrous beings from another universe came out of. On the up side, though, traveling through the Fractured Lands doesn't mutate you as horribly as Torque.
Dungeon Punk: Magic, referred to as "thaumaturgy", is commonplace and used by practically every skilled profession.
Perdido Street Station has the slake-moths — monstrous, insectoid creatures that devour minds. Not literally, what the creatures feed on is the very sentience of their prey itself, leaving their victims utterly mindless shells. How terrible are these abominations? At one point, the government of New Crobuzon attempts to strike a deal with Hell to get them to intervene and stop the threat, and the demons are too frightened to get involved.
The Weaver, who the New Crobuzon government turns to when the demons turn them down. It's a gigantic spider that exists between dimensions and is capable of traversing them as easily as we could walk down the street. It is also batshit crazy, speaking in the "flight of ideas" style most often seen in unmedicated schizophrenics and capable of doing anything to anyone, friend or foe, merely because it seems "fitting". During the brief time that the heroes are in its presence, the Weaver cuts off the ear of everyone in the room for reasons known only to itself. It also repaired the ears of some of the people, again, for reasons unknown. The Weaver encountered in the book has an obsession with scissors, and happily accepts them as gifts, if the term 'happy' can be applied to it. Apparently it enjoys collecting things in general, as it is mentioned that before its obsession with scissors, it collected chess sets.
And then there is the Torque, described by one character as a tumour that aborted itself from the womb that produced the forces of Birth and Death. Whilst not evil per-se, it is a natural force that is almost totally uncontrollable which warps and mutates matter and biology into horrifying things. Merely trying to research it can turn you into an Eldritch Abomination. It was once used as a weapon; the results of the Torque Bomb were so awful even after a generous application of Magitek versions of nuclear weapons there's a country-sized region of the world which isn't going to be inhabitable by anything but abominations ever again.
To elaborate on the 'horrendous mutations' part, at one point Isaac Dan Der Grimnebulin pulls out a book of photos taken at ground zero of the inhabitants (Though it may have been implied that there could be survivors) to show to a client.
Isaac: "Turn the page, Yag. This next one, no one has the slightest idea of what it used to be. But I think those gears are descended from train engines. The... uh... best is yet to come. You haven't seen the cockroach-tree, or the herds of what once may have been human.
Oh, and in the middle of a city there are The Ribs, the partially exposed skeleton of some enormous creature that has been dead for a very, very long time. Attempts to build over it resulted in seemingly structurally sound houses that just fell apart and tools that break long before they should, and attempts to excavate the whole skeleton tended to result in the workers suffering horrifying nightmares, or disappearing suspiciously. It was decided that whatever it is is best left buried and uninvestigated. Notable in that even the slake-moths felt that being around The Ribs was unsettling.
Then in The Scar, the second book in the series, there's the avanc, an entity from another universe big enough to tow the floating city, Armadanote Armada is only a couple square miles on the surface, but has layers and layers of decks and bridges. A single vein is as large as a 20-foot ridge. Imagine how big that must be! Better yet, imagine just how big the stuff that preys on the avanc in its home dimension could be! All that anyone knows about the avanc is that it swims and has at least one thing that could be described as a limb. (Assuming the mind-bending hypothesis about how it's really some sort of microscopic plankton at home, and it becomes unimaginably huge due to transplanar warp when it enters Bas-Lag, is false.)
"Colourbombs" in the same setting are implied to be less wrong but even more destructive; Mieville's influences being what they are, this latter might bear some relation to "The Colour out of Space". Colourbombs were used to cover up whatever the Torque did to Suroch. Basically, it was better to blanket nuke the area than try to explain the effects of torque to the populace of New Crobuzon.
The city-killer (aka Hecatomb) in Iron Council is beyond even colourbombs for sheer alien annihilation. It erases cities. And casts ripples of destruction backwards in time.
Golem: Bas-Lag has a magical discipline called "golemcrafting", wherein magicians channel power into anything that isn't living. Most of the Golems created are fairly standard (blade, flesh, metal, clay, wood), However the main character of Iron Council creates increasingly more fantastic golems some of the more memorable ones being: poison, light, dark, and TIME.
Good Powers, Bad People: There are professional magic users, Thaumaturges, some of whom have impressive healing powers as well as the ability to perform transplants/surgery without risk of harming a patient. Unfortunately, this is a Crapsack World, and many thaumaturges with such powers are vile sadists. Instead of using their powers to heal, they play a role in the legal system, Remaking criminals as punishment for their crimes (i.e. painfully turning them into horribly disfigured biological or technological mash-ups).
Handlingers, being the size of human hands, are rather conspicuous and conceal themselves on their host bodies by hiding under large articles of clothing.
They come in pairs of left and right hands, left hands known as sinstrals and right known as dextriers. Dextriers are considered to be the warrior caste because they have the ability to fly and "spitsear" (breathe fire) when controlling a host's body. Sinstrals are the leader caste because they have the ability to shut down a dextrier's ability to control a host.
Although they have psychic abilities, the native language of handlingers involves them extracting themselves from their host bodies and exchanging information by crawling and slithering over each other in an orgy of hands and tails.
Spiral Jacobs, the vagabond, roams around the city of New Crobuzon and spends his days vandalizing the city with drawings of spirals. This occurs during a time of political unrest, and the masses of New Crobuzon adopt it as a symbol of the rebellion, wearing it on their clothing and making the marks themselves. Subverted in that Jacobs is actually the ambassador of an enemy city and the spirals are part of an extremely powerful and intricate magic that would completely destroy the New Crobuzon, sending ripples of destruction backwards through time.
Laser-Guided Karma: Deconstructed - Remaking is supposed to be like this. Unfortunately, it usually just leads to (implied) Mad Artists fucking around with the body and inflicting crippling Body Horror for the fun of it. Case in point, there's examples of taxi Remade who are sometimes 'both cab and beast of burden'. A particularly cruel example would be a woman who smothers her baby has her baby's arms attached to her face so that she'll never forget what she did. It leads her to become a terrorist and kill the mayor. Oops.
Machine Worship: The Construct Council in China Mieville's Perdido Street Station. A massive AI in a scrapyard with worshipers. However it still has to communicate through a dead body hooked up to it. As they leave Isaac notes that for the spokesperson to work, they must have been alive when they were hooked up. Also in the gap between this and the sequels The Scar and Iron Council, there is a purging of all constructs from the city for fear of what they could become.
The Magocracy: There are passing references to a nation called "The Witchocracy" in Iron Council, but it's not explored in great detail.
Mega City: New Crobuzon is enormous enough to be considered its own state, and is even at war with another city in Iron Council.
Mermaid Problem: Neatly tied up when it comes to the Khepri. Weird bug head, sexy lady body. For some reason.
Never Recycle a Building: Inverted. Not only will abandoned properties not be left unoccupied, but they're prone to be recycled as something radically different: an old city residence as a pork slaughterhouse, a tanker ship as a prison, a flatbed train car as a mobile graveyard.
New Weird: One of the seminal — and most commercially successful — works of the subgenre, in fact.
Non-Mammal Mammaries: There are many different types of xenian characters, some of which fall under this trope. It's averted with the vodyanoi and garuda, which procreate like humans, but are flat-chested and not very sexually dimorphic by human standards. Cactacae females, on the other hand, lay eggs in the ground that the males fertilise (don't think about that too much) and suckle their young. The most bewildering by far are the Khepri species, introduced in the first book. The men are beetles—literal beetles. The women, on the other hand, are red-skinned human women with beetles for heads. As a result, khepri women have sex with humans, or even other female khepri when given the choice. Khepri reproduce by allowing the males to mate with their heads.
Oh My Gods!: Human residents from New Crobuzon mostly all swear to the same deity, Jabber, using the stock phrases like "By Jabber..." and occasionally mixing in the lowercase "god" for flavor.
The ab-dead are stronger and faster than the living. They have forked tongues and can move almost imperceptibly in shadow. They heal quickly and do not age. Sunlight does not kill them immediately, especially older and stronger vampirs, but it severely harms them and prolonged exposure will kill the ab-dead. Vampirism is caused by a virus in their saliva, and although infection is not guaranteed, repeated direct feedings can cause a human to become ab-dead.
The ab-dead live in secrecy throughout Bas-Lag except in Armada and High Cromlech. In Armada, the Brucolac and a cadre of his closest allies are the resident ab-dead and run the Dry Falls riding. Dry Falls is an area and political standing within the governing structure of Armada; residents of Dry Falls enjoy more political weight, subsidized entertainment and lighter disciplinary actions than other ridings, but pay for this with the gore-tax, a routine collection of blood from Dry Falls residents. In High Cromlech, the city of the dead, the ab-dead live in the open, but make up the lowest class, even below that of the living. The dead of High Cromlech protect the living from the predations of the ab-dead, and therefore, ab-dead are reduced to begging for handouts from the living and are considered to be junkies.
Ab-dead is just the term for undead, in keeping with the frequent use of the prefix ab- instead of un- in the Bas-Lag books. Vampirs are just one form. As noted, in High Cromlech the ab-dead rule, but the vampirs, kind of considered not real ab-dead because of their parasitic nature, are on the lowest social rung.
Phantasy Spelling: China Mieville employs this trope heavily in the Bas-Lag Cycle — vampirs, alchymy, chymistry, elyctricity...
Pyrrhic Victory: Frequently throughout the novels. In fact, its the ending to every single novel. While the stories frequently have demoralizing endings, there is usually some spot of success.
In Perdido Street Station: Isaac has saved New Crobuzon, defeated the Slake Moths, proved his crisis engine will work (and more importantly, kept it out of the hands of the Corrupt Government & the Mecha-Mooks), and hardest of all, survived. On the other hand, Lin is lobotomized, Yagharek is revealed as a rapist, Isaac refuses to help Yagharek, and the Constructs are headed for destruction. Not to mention Isaac and Derkhan have to flee New Crobuzon with the lobotomized Lin in tow, as the government is understandably not interested in giving them credit for having saved the city and has left them at the top of the Most Wanted list.
In The Scar: Bellis fails in almost every endeavor she sets out to accomplish, which includes preventing the avanc from being summoned, saving New Crobuzon from an attack (which actually didn't exist), and preventing a civil war from breaking out between the citizens of Armada. She does manage to get back to New Crobuzon by the end, and she has shuffled off a lot of her unconscious, self-interested naivety in the process. As a plus, she's pretty much the only character who interacts with the Grindylow and doesn't end up brutally murdered. This is the happiest ending of the three novels.
In Iron Council: It all goes to hell. Counting all the horrible betrayals, Senseless Sacrifices, and Face Heel Turns in the novel would take up more room than a spoiler tag could conceivably hold. Suffice it to say that by the end of the novel, the Iron Council does not technically die in their Bolivian Army Ending...but they don't win either. Some readers felt that Mieville intentionally destroyed as much as possible to bring closure to the setting.
Reality Is Out to Lunch: The Cacotopic Stain, an area of desert (well, it's desert now) which is completely consumed by a Torque storm, and Suroch where New Crobuzon dropped a "torque bomb" in a past war. The way they're described, they're part nuclear wasteland, part half-opened door to the abyss.
Schizo Tech: The novels are set in a world that is roughly late-Victorian in technological terms with steam power being the driving force of industry and neon lights and phonographs being recent inventions (though firearm technology is still largely stuck at the "flintlock" phase), but also has robots and a long-defunct weather control machine. Justified in-universe, in that it's implied that the world was more advanced centuries ago, and in fact many "new" inventions are merely rediscovered.
Starfish Language: The Dead communicate with coughs, grunts and silence, khepri use sprayed pheremones to talk, handlingers have strange slithering psychic orgies and constructs speak to each other with math. The construct council actually needs an avatar to communicate properly with the protagonists.
Tomato Surprise: The short story "Jack" is narrated by someone who claims he helped Jack Half-A-Prayer, the Remade vigilante, become the legend he was. He did, too: he's a New Crobuzon prison orderly, who once assisted the biomancer who replaced Jack's hand with a giant mantis claw.
Weird Moon: The moon is mentioned to have two moons of its own.
Wild Magic: The Torque is somewhere between this and The Virus. Yagharek in Perdido Street Station hears a rumor that it can supposedly be used as Functional Magic, but nothing could be further from the truth. In reality, every effort to control or harness it inevitably leads to some form of Body Horror.
Winged Humanoid: The Garuda are humanoid avians, though much more bird-like than person-like. A major character in the story is a garuda whose wings were cut off; he visits the city of New Crobuzon with the intent of finding someone to grant him flight again.
Wretched Hive: New Crobuzon blows almost everything else out of water in terms of sheer ugliness. It's ruled by vicious capitalists who ignore crime against ordinary citizens, but send death squads to deal with dissenters, essentially ensuring that the city stays a brutal lawless mess forever. Criminals, even ones guilty of small-time theft, are punished by mutilating their bodies in horrible and ironic (in reference to the crime) ways.