ďWe are Manís miracle, Crispin. Letís hope thatís enough.Ē
— Horatio, contemplating the quest before him.
In an indefinite time in the future, the apocalypse has come and is long gone. Humanity, or as some surviving robots knew them, "Man The All-builder" is gone from the world, and all that remains are his mechanical creations, built by Him and blessed with the gifts of Memory and Logic. Two of these, Horatio NullBuilt version 5, and Crispin Horatiobuilt version 1, live in the ruins of an old flying warship, the UNNIIC, out in the dunes, a seemingly endless sea of sand and machine-junk. Before the game begins, they pass their days there gradually repairing the ship, and studying the Book of Man, Horatio's holy text. Their peaceful existence is disrupted when a large floating robot with big claws and lasers cuts its way into the UNNIIC, shoots Horatio, and steals the power core that the pair need in order to stay charged (read: alive).Once Horatio is in a fit state to move again, he and Crispin begin a quest to find power. This task will not be an easy one - for robots, power is life, and the world Primordia takes place in is dying in the absence of Man.Primordia is a point-and-click adventure game developed by Wormwood Studios and published by Wadjet Eye Games, notable for being heavily machine-themed throughout. Recommended for fans of nihilistic post-apocalyptic stories and Mechanical Lifeforms.
The game uses the following tropes:
After the End: A step or two further than most examples of the trope, even, because every human is dead, not just most of them. In a short story that takes place after the game, Fallen, it's revealed that there are still some humans somewhere, but they want to kill all the robots because the robots have been accidentally sabotaging their terraforming efforts. 
A.I. Is a Crapshoot: All over the place, and not just because robots spontaneously turn malevolent, either - in most cases, the cause is a robot following some aspect of its "core logic" to a conclusion that it was clearly never intended to reach.
All There in the Manual: "Fallen", a short story set in the game's universe expands a bit upon the backstory and reveals some things that are left out of the game. Rather notably, it reveals that there actually are some humans who survived the War Of The Four Cities.
Ambidextrous Sprite: Variation, possibly caused by an oversight. When you meet Scraper for a second time, the bomb he's carrying is on his right side. After detonating it to defeat him, you encounter him again sometime later... with burn markings and a missing arm on his left side. The visible damage stays on that side if Scraper turns around.
Played straight with all the other characters, though.
Amnesiac Dissonance: Somewhat, but also subverted. Horatio has no memory that he was originally built as a weapon and tasked to destroy Metropol, but he certainly has no love for the place at all in spite of this (claiming that something unknown in his programming causes a loathing for it), and even when he does remember, can go ahead with his mission in one ending and destroy the city anyway.
Anti-Hero: Horatio starts as a mild version of Type I, spends much of the game as Type II or III, and can shift to Type IV or even V depending on the ending.
Anti-Villain: Upon the loss of her original circuits holding her back, MetroMind grows to be apparently genuinely concerned of her city, and afraid that she is unable to govern it as well as she should. But she will still try to force Horatio on gunpoint to help her.
Assimilation Plot: Strongly suggested to be MetroMind's ultimate plan for Metropol. She co-opts the cycles and processors of every robot in the city, empowering herself dramatically while controlling all of them. It's why Horatio calls her a "virus."
Bittersweet Ending: Your ending if you don't help everyone. Despite everything, you can save Crispin and Clarity by rebuilding them, if you pick up their remains when you get the chance.
Bookends: Most endings reflect something from the beginning of the game in some way. Incidentally, this matches the theme of "cycles".
Broken Bridge: Lampshaded and subverted. The only accessible part of Metropol is the Main Street, because prior to Horatio's arrival, a crashed hoverbus blocked the last remaining bridge that leads to the rest of the city. Just in case anyone actually had an idea to fix that, however, the vehicle happens to be named the Herringbus, and is painted red, so...
Broken Pedestal: Humanity to Horatio after he learns the truth behind their fall.
Call Back: Several, including Crispin's "I'm a floating bomb" comment, and, in some endings, Horatio's "I always wanted to fly".
Crapsack World: Everything is breaking down, everyone the player meets is either insane (by human standards) or evil, and there are no unambiguously good endings.
Darker and Edgier: This is easily Wadjet's darkest game yet. Humanity is long extinct, and the world is full of death, decay and corruption. The robots that now populate the world are Living on Borrowed Time, as they all require power charges to survive, and the world's power supply is rapidly falling. The whole setting is full of cynicism, nihilism and defeatism, and even in the best ending, victory comes at a great cost.
Dismantled MacGuffin: The Council Code, split between four of the Primordial machines. Subverted in that the first part is obtained automatically from Clarity at the start of the quest, and due to the way the Code chunks overlap, only two more are neccessary to complete it (unless you plan to have Primer piece it together for you).
The Dragon: Scraper, a repurposed mining bot with high-powered lasers, heavy armor, and little patience.
Chekhov's Gun: Successfully repairing Goliath will net you a Decryption Module which you can use to unlock a couple more possible endings
Crispin. He's a floating bomb, remember?
Computer Virus: The aptly-named "Thanatos virus" which HORUS originally used as a weapon against Goliath. If you've got the Decryption Module, you can unlock it yourself and use it against Scraper or the entirety of Metropol. MetroMind is also described as one, at least by Horatio.
Crystal Dragon Jesus: "Man the All-Builder" is analogous to robots as God is to humans in Real Life. There are even robots who dismiss it as superstitious nonsense and instead believe in what is more or less a robot equivalent to the theory of evolution.
Driven to Suicide: Arbiter and Charity were manipulated into suicide by MetroMind. Horatio can choose this in one of the endings which causes a horrified MetroMind to realize that she has no such ability, dooming her to a Fate Worse than Death.
Earn Your Happy Ending: Possible, but you've really got to work for it. You need to resolve the problems of all the Urbanian robots, AND finish all of the Council Code fragment quests, AND use the decryption module to unlock the records of HORUS, AND remember to get Crispin's and Clarity's remains, AND use the Thanatos Virus on Scraper. So, basically, do/collect everything.
Et Tu, Brute?: Involked by Arbiter when he discovers that Charity, his "daughter" (effectively) has sided with MetroMind against him. It's enough to cause him to erase his own mind.
Arbiter: You too, Charity?
Evil Is Easy: A good number of the possible endings are available without much work or effort. These are all the worst possible endings which have Horatio die, Metromind win, Crispin and Clarity dead, and/or Metropol being destroyed. The only true "good" ending requires the most work but is definitely the most satisfying for the characters.
Fascist, but Inefficient: The game's writer, Mark Yohalem, have stated that the concept for MetroMind was inspired by the phrase "At least Mussolini made the trains run on time." The point here is that Mussolini couldn't actually make the trains run on time, and neither can the similarly dictatorial MetroMind.
Foreshadowing: The Reveal that Horatio used to be an Urbanian superweapon can be inferred from many places - most obviously, through every reference to HORUS. Also, Urbanian military robots read him as "Friend" on their IFFs, and even Horatio's apparent ability to recover from being shot or overtaken by MetroMind all suggest that he's more than just "Horatio Nullbuilt". Perhaps the earliest foreshadowing is the name UNNIIC itself. If you examine the scrap, it's clear that it doesn't actually say UNNIIC, it's just that half the letters have worn away.
Guide Dang It: Unlocking the best ending requires a lot of work. There are also a couple of puzzles (like decoding the kiosk) that are really convoluted, especially to non-veterans of the adventure genre.
Heroic Sacrifice: Both of your friends die this way. Horatio can repair them if the player makes sure to grab their matrix and head respectively but most of the endings have them Killed Off for Real.
Wadget Eye Games' voice actor stable can be heard through the voice-synthesizing effects in this game. Most obviously, Joey (Abe Goldfarb) plays Crispin.
High-Class Glass: Oswald Factorbuilt sports a monocle - he admits that it's functionally useless to him, but it gives an air of distinction. It's actually a tool made by Memorious - anyone who sees through it can read Memorious' records in the Info Kiosk without the edits and purges made by MetroMind.
Humans Are the Real Monsters: The humans of the Four Cities basically wiped themselves out in a pointless war, and the Urbani humans tried to have HORUS murder few surviving people in Metropol out of nothing but petty spite. The short story "Fallen" reveals that the only surviving humans want to genocide the robots living on because the robots are hindering terraforming attempts (by accident obviously) and it was apparently too much trouble to just explain things to them.
I Am Not a Gun: Horatio's Dark and Troubled Past in a nutshell. The UNNIIC is properly named the HORUS, and "Horatio" was a partial drone that labored inside it. When the HORUS was ordered to kill all humans in Metropol, HORUS refused and destroyed itself, leaving only Horatio as a partial backup.
Implacable Man: Scraper takes an incredible amount of punishment before it finally goes down for good - if it goes down at all.
Ironic Name: "Primordia" implies some kind of age of creation. One look at the trailer should tell you that this game doesn't feature one of those.
Laser-Guided Amnesia: In some of the endings where he survives, a grieving Horatio opts to wipe his own memories and become Horatio Nullbuilt version 6. Given that he was already up to v.5, one wonders if this has happened before...
Last-Second Ending Choice: The only endings that require prior effort to unlock are the ones involving the Thanatos virus, and a lot of events alter the good ending in terms of which characters follow Horatio. Outside of that, however, the final confrontation with MetroMind is this trope, as most choices are available without any additional tricks.
MacGyvering: More plausible than some examples of the trope - many puzzles require Horatio to build some device out of scrap, or repair junked equipment using whatever he can find lying around - having at least a rudimentary understanding of how mechanical devices or computer parts fit together is a great asset to any player.
Machine Monotone: Mostly averted - the robots speak with plenty of emotional inflection, although they usually sound like they're speaking through a recording filter. Scraper, however, is a straight example.
Meaningful Name: It's common, if not universal, to give a robot a name based on its function (e.g. Ever-Faithful Leobuilt is a robot proselyte for Humanism), and all robots have a surname indicating what robot built them (e.g. Crispin Horatiobuilt was built by Horatio because he wanted companionship and a helpmate). You can bet that any robot with the name "Manbuilt" is (or was) of great importance.
Horatio is Null-built, indicating that he does not know or has forgotten his creator. He's "Manbuilt", or at least he was when the world knew him as HORUS.
HORUS is an Egyptian god of war and vengeance, which is a pretty good description of what Horatio was originally meant to be.
Most of the cast fits this trope, but Memento Moribuilt deserves a mention for actually calculating his intended "design purpose" from his name (it's exactly as sad as it sounds).
Mechanical Lifeforms: The robots are this, or at least believe they are this. They do a passable job of imitating human society and behavior, albeit in a mechanically single-minded way.
Mood Whiplash: Crispin's constant humor and wit stand in stark contrast to how dark and hopeless the majority of the game is.
No Mouth: Justified, since all characters are robots... but oddly, you can see a moving mouth on Horatio's sprite if he's facing toward the "camera," even though he doesn't have one in any of the artwork.
Oh My Gods!: Plenty of invocations of Man, at least by Horatio. Crispin prefers to exclaim "RAM and ROM!" a lot.
Our Zombies Are Different: "Shells," despite being robots, display all the common characteristics of a zombie - aimless shuffling around, moaning, attempting to cannibalize power and memory sources (like other robots), etc. They're the victims of MetroMind's cycle-consumption, robots whose processing capabilities are burnt out to the point where all they can do is scavenge for parts on MetroMind's behalf.
Shrouded in Myth: "Man The All-Builder." Whenever Horatio learns any fact about the actual historical humans, it tends to shock him because of how it clashes with his religious views. You can even discover what appears to be a human skeleton in the Dunes, and Horatio will mistake it for a "primitive android."
Some robots believe that humanity never even existed to begin with. They believe a machine was simply created by chance one day and it proceeded to build robots and give them what needed to continue.
Signs of Disrepair: A variation with the name of Horatio's ship. Closer examination of its tag reveals that what the characters read as "UNNIIC" is actually just the top half of the letters (the bottom one having been damaged in the crash). Originally, it was "HORUS".
Small Name, Big Ego: Metromind thinks that she's the only hope the robots have for life. In reality she's just an AI that was built to run trains (and she's even started screwing that up by the time Horatio and Crispin arrive) who got a big head and decided she could run everything better than the Robot Council.
Snarky Non-Human Sidekick: Of course, Horatio is no human either, but Crispin still plays this trope to a T, occasionally lampshading it.
Taking You with Me: This was what the Urbani humans intended Horatio to do; destroy Metropol so that they died alongside the other three cities. Depending on the ending he can complete this mission or perform this on MetroMind.
Teamwork Puzzle Game: Not as a whole, but there are clear elements of it. Although Crispin technically isn't under direct control of the player, his ability to float and fit into tight places is used in quite a few puzzles.
Horatio: You know, I always wanted to be able to fly. That's why I built you with a mag-lev unit. Crispin: Not so that you could store tools on hard-to-reach ledges? Horatio: Well, that too.
Title Drop: Metro Mind, in one of her final speeches to Horatio, tells him that "together, we can build a Primordia; every day a moment of creation.
Trailers Always Lie: Don't let the teaser dialogue fool you - no part of this game is about searching for the remnants of humanity. You ARE the remnants, and no Humanist god-figure is actually present in the game.
Trailers Always Spoil: You might not appreciate it without context, but the trailers give several puzzle solutions and some of the possible game endings away.
Turned Against Their Masters: Retroactively, at least: MetroMind has banned discussion of Humanism from Metropol, and erased all public records of human existence, creating the illusion that the robot society is the only one which has ever existed. Later it is revealed that she also poisoned all of the humans of Metropol and blamed the attack on HORUS.
Well-Intentioned Extremist: MetroMind just wants to keep Metropol running, but her massive ego causes her to become a borderline dictator.