Spearbreakers provides examples of the following tropes:
Abnormal Ammo: Mugs are suggested, and even dwarven children, to combat Spawn and Manamaids. These are suggested to serve as ammo for catapults.
Aborted Arc: Was originally intended as a Fan Sequel to Syrupleaf; however, this aspect was gradually dropped as the fort developed its own narrative, only showing in the form of occasional mentions of Parasol.
One overseer, Tomio, is basically an automoton, though he has another name for it.
Parasol employs mechs and mechsuits in its forces.
Anachronism Stew: To an extent, logical technological development is completely ignored, and the timewar companies have mechs, jetpacks and VTO Ls, but no fixed-wing aircraft. Spearbreakers also cobbles together multi-dimensional portals, time travel, and medieval warfare.
And I Must Scream: Softa, Ashsaber and Mad-Dok's consciousnesses remains trapped in their mind, unable to influence the body. Softa barely clings to her sanity by virtue of Fischer, Splint among others visiting her. Ashsaber is not known to Spearbreakers itself, though canon says he is a gibbering wreck. Mad-Dok is that one spawn that never screeches. Just looks. Creepy indeed.
Anti-Climax: Mitchewawa promised us he would invade hell during his turn. He didn't.
Mr Frog, though technically a good guy, would make a pretty wicked villain.
Talvi is also technically a good guy/girl, but she eventually becomes the antihero of several story arcs.
Anyone Can Die: In most Dwarf Fortresssuccession games, people embrace the fact that their characters can die at any moment. Due to Spearbreakers' canon style, the writers made sure the overseers avoided deaths whenever possible, but even the best efforts were often futile.
Colonel Badass: Colonel Fischer - it's scary how powerful the leader of the army became, racking up over 200 kills by Splint's second reign. Not only that, she was this Bad Assbefore she was sent to the danger room.
Conditioned to Accept Horror: This is every dwarf in Spearbreakers. Early on, Ashsaber and Softa transformed into Holistic Spawn, and were locked away in "isolation chambers", screaming their hatred for the living all hours of the day. These chambers were right across from the living area - the dwarves had to learn to sleep through it.
Hanslanda: "Oh god, everyone in the fort is heavily medicated and boozed up just to deal with backround noise. That's a bit hardcore."
Continuity Snarl: There are multiple contributing authours, and their individual plotlines often don't quite match up with each other.
Creepy Cemetery: The Clover contains hundreds of unmarked graves piled together. Dwarves are forced to pass it on their way to the forges. Simon Tam's room is beneath it, too.
Crossdresser: Bombzero was actually a man. However, he's noted in the records as a woman because you'd never know he wasn't.
Deadly Training Area: Mr Frog put together an advanced-tech "combat simulation chamber" to rapidly hone the abilities of the militia. This was a subject of controversy among the overseers. Also averted, in Reudh's Spawn Containment Facility. Marksdwarves can engage Spawn in combat in complete safety. Doesn't stop civilians urinating themselves in terror whenever they pass by, though.
Groin Attack: Vanya attempted this against Tomio, to try to escape him.
Heartbroken Badass: Splint's love, Stova, died after the initial Spawn attack. Splint redirects the pain towards the Spawn as hatred.
He Knows Too Much: Not really that much of a surprise, given Spearbreakers' conspiracy setting.
Mr Frog is exiled from Ballpoint pre-story because of what he knows.
Joseph and Mr Frog separately try to kill Vanya because of what she's seen.
Mr Frog tries to administer an amnesiac to Talvi to force her to forget what she's seen, and later obtains the assistance of Joseph for that purpose.
Heroic Sacrifice: Sus sacrificed his life on the spikebridge to save the last people who were coming in from outside. Interestingly, Sus II got a broken spine from that same bit of Malevolent Architecture.
Honor Before Reason: Sus II, after having been critically injured in a goblin attack, recovered, and was then critically injured again in a spike mishap. He still trains as a soldier despite having a BROKEN SPINE, making him a paraplegic. He lies on the ground attempting to train.
Mincer also refused treatment on his torn hand. His wife, Uvash, attempts to carry out orders despite missing her left foot.
Last of His Kind: Mr Frog is apparently the only survivor of his species in the Shared Universe, though not, perhaps, The Multiverse. He's described as being a dwarf-sized gnome, though he perhaps has an inch in height above the average dwarf.
Living Shadow: Rose's pet/companion, Halen. This causes a great deal of confusion as everyone seems to have a problem with it, treating its induction into canon as Serious Business.
Low Culture, High Tech: Eventually the Spearbreakers dwarves come across the timewar technology. Urist, Vanya, and Hans play around with it quite a bit.
MacGyvering: Mr Frog excels at this, creating bombs and weapons from spare lab equipment.
Mad Doctor: Kannan especially, but technically, any of the hospital staff could qualify as this.
Mr Frog is notorious for his experiments, which have little regard for morality. However, he's not precisely "mad"... At least, not most of the time.
Draconik Sankis claims this title with the creation of the Spawn of Fischer, as well as resurrecting Jack Magnus twice. Like Mr Frog, he's quite a bit saner than most of the other residents. It's ironic that in Spearbreakers, the mad scientists have more sense than everyone else.
Aussie Evil conducts unusual experiments with blood, greatly enjoying its taste and trying to "improve upon it". He's without a doubt the most "mad" of the three.
Malaproper: Talvi has a tendency to use phrases that don't make any sense at all.
Manchurian Agent: Vanya, the skulker, was what became known in the canon as a "Sleeper Agent" of Parasol, i.e. the person's agent side "sleeps" until "awakened", and they have no knowledge of that aspect of their lives.
Pyrrhic Victory: The first Spawn siege in Reudh's reign resulted in NINE deaths, and two cripples. Additionally, Mad-Dok was infected with the Spawn Fever. The second Spawn siege in the same year resulted in two more, including Jack Magnus.
Mr Frog isn't quite 700, but he's well past three hundred.
Scylk is pretty old, too, especially by terrestrial standards.
Reforged into a Minion: Holistic Detective's Spawn can turn bitten dwarves into more of her toothy minions. This has happened to many over the nearly ten years; among them is Stova, Splint's lover and one of the founders of Spearbreakers, Softa and Ashsaber, both militia, and Mad-Dok, auxiliary militia. Softa, Ashsaber and Mad-Dok are cooped up in holding cells designed by Mr Frog.
After the first couple of years, Talvi became obsessed with Mr Frog, believing she was in love.
Lord Reudh has a creepy yet adorable crush on Rose, Splint's bodyguard. This is later determined to be an unusual aftereffect of Mr Frog's chemical concotions. After this, a single kiss from Vanya Carena is enough to make him fall in love with her, determined to follow her to the ends of the earth.
Strange Salute: During Draignean's reign, a punch to the face (the stronger the better) becomes the Spearbreakers salute.
That Was the Last Entry: This happens after Vanya's twenty-fifth journal entry. It's misleading because she's not actually dead.
The Alcoholic: Earlier in the story, Mr Frog was always calling for his Merlot.
This Way to Certain Death: Migrants coming to the fortress have to pass by the rotting corpses of other migrants that were left outside to die in the middle of sieges. Caravans have to pass the remains of caravans that didn't quite make it to the depot.
Time Travel: Loads of this everywhere, even though some people protested it. The timestream eventually becomes such a mess that it's a great big Timey-Wimey Ball. Somehow, everything still makes sense.
Took a Level in Badass: Dauros, one of Fischer's squaddies, started off relatively strong, but is nearly as strong as Fischer herself. Dauros managed to KICK A SPAWN'S HAND CLEAN OFF.