The Dungeon Anarchist's Cookbook recap

The fourth floor is the Iron Tangle, an endless lethal subway network. Carl, Donut, Katia, and Mongo earn a shared personal space, and a prize machine gives Carl the Dungeon Anarchist's Cookbook, a living manual of sabotage written by past crawlers, while locking Mordecai out for a critical week. The party deciphers the trains' looping geography with help from NPC crew members and allies like Elle, Imani, and Bautista, as a system-wide plague of festering ghouls begins overwhelming the lines. Hekla's Daughters arrive seeking help rescuing a thousand stranded crawlers; the mission succeeds, but Eva's cruelty drives Katia to accidentally kill Hekla, who survives only through Donut's resurrection spell, exposing Hekla's plan to poach Donut. Frank Q gives Carl a dying warning about Maggie My before being killed by Chris. Carl maps the Tangle's true shape, organizes mass evacuations through the trainyards, survives a battle where the war god Grull is summoned and banished to the Abyss, and coordinates the simultaneous destruction of every ghoul generator, saving the surviving crawlers. Zev is taken for re-education, and Donut picks the party's sector for the fifth floor.

Previously: the alien Borant Corporation collapsed civilization and turned Earth into an eighteen-floor broadcast dungeon. Carl and his ex-girlfriend's talking cat, Princess Donut, survived the first two floors, became stars of the galactic feed, and gained the guide Mordecai, the pet dinosaur Mongo, and enemies including the Skull Empire's Prince Maestro. On the third floor Carl became a Primal Compensated Anarchist and Donut a Former Child Actor with Mordecai bound as her manager. They freed the Elite NPC Signet from the corrupted circus of Ringmaster Grimaldi, unraveled a murder mystery that ended with the magistrate's gatekeeper Miss Quill dead and her doomsday ritual, The Final War, tearing the floor apart, and escaped the cataclysm Carl himself contained by sealing a leaking soul gem. The doppelganger crawler Katia Grim joined the party. They reached the fourth floor on the leaderboard, carrying a bounty, warned by Odette about the war god Grull and about Hekla, leader of the Daughters, who wants Donut for her own team.

The fourth floor is the Iron Tangle: a vast, decaying subway system where every station teems with monsters and the trains themselves are deathtraps. Donut opens the floor by taking the Football Hooligan class, keeping her old class skills. Fighting off the initial onslaught, the party earns a stack of achievements, and a special reward grants Carl, Donut, and Katia a shared upgraded personal space with beds, a crafting studio, and a training room, which Mordecai teaches them to use. Carl learns that a last message from Brandon of the Meadow Lark group means the Andrews brothers' story has ended badly. Setting up his alchemy, sapper, and engineering tables, Carl begins manufacturing ordnance in earnest while the party works the colored lines, clearing stations and picking up the first hints, from the NPC Vernon, of how the trains loop, reset, and connect to distant yards.

Mongo reaches his full adult size, and a prize carousel triggered by Carl's fan box changes the floor's course twice over: it puts Mordecai in a seven-day time-out, locking him out of the party's safe rooms, and it gives Carl the Dungeon Anarchist's Cookbook, a living manual of sabotage compiled by generations of past crawlers, which also unlocks the party's sponsor tab. At the Desperado Club the party hires the rock-monster mercenaries Bomo and the Sledge and reunites with Elle and Imani, surviving an attack by desperate crawlers inside the club itself. They learn that every fifth station houses a boss-grade Krakaren clone. Carl derails a train, narrowly avoids a summoning of the war god Grull when the engineer turns on them, and picks up a sponsorship from the Valtay, with Donut and Katia gaining royal sponsors of their own. Katia's beheading of a war mage with Donut's Hole spell announces how dangerous the quiet doppelganger is becoming.

The party begins to crack the Tangle's geography. Carl survives a deliberate collision with the Nightmare Express to reach its cab, befriending its crew, and discovers through portal analysis that the souvenir hats handed out on the trains allow teleportation to the trainyards at the ends of the lines. A crawler information-sharing network takes shape. The floor, meanwhile, is getting sicker: the monsters are in withdrawal from a drug the system supplies, and as the stages progress, creatures that fail to survive become festering ghouls that swarm the lines and yards. The party learns the terminus stations are disguised mimics, dooming crawlers who treat them as exits. Bautista's group grinds toward one anyway, Elle and Imani's team maps escape routes, and rescued NPCs fill in fatal details. Quan Ch's rampage strands entire teams, and Carl's plans shift from survival toward mass evacuation.

At the Desperado Club, Carl meets Frank Q one final time: the dying player-killer gives him a parting gift of information that recasts the murders from the first floor and warns him how dangerous Maggie My truly is. Frank is killed soon after by Chris, once of the Meadow Lark group. On a sponsored television appearance Carl exploits a staging area to loot shamelessly while Donut charms the audience. Then Hekla's Daughters arrive, asking the party's help to rescue a thousand crawlers, including Li Jun's team, stranded deep on a contested line. Using Katia's body as a plow, the rescue train smashes through ghoul-choked stations, but Eva's relentless taunting of Katia ends in horror: Katia's panicked Rush skill splatters Hekla against a wall, and only Donut's Second Chance resurrection spell brings her back. In the aftermath the party pieces together Hekla's real plan, to recruit Donut, and the alliance dissolves into wary hostility. Carl's team splits off to rescue Bautista while Li Jun takes the survivors toward a last stand alongside Imani.

Katia emerges from the rescue transformed: showered in rewards, she is now among the highest-leveled crawlers in the dungeon, second only to Quan Ch. The party gathers souvenir hats and line keys from the dead, and with the NPC Growler Gary works out a rescue architecture for the crawlers stranded at the Abyss: paired interdiction carts to sweep the lines clear and carry survivors to the trainyards. Carl blocks a ghoul-infested line by sending a train packed with explosives down it, but elsewhere a crawler attempt to disable a generator detonates a soul crystal, and the dying monsters begin bursting into swarms of fast-growing Krakaren spawn. The rescue at the Abyss partially succeeds, moving hundreds of crawlers to the yards. Mordecai finally returns from his time-out, and Katia, studying the maps, works out the Tangle's true shape, the key to predicting where the exits will be as the floor enters its final days.

The endgame arrives: the stairwell stations connect to the far half of the Tangle just as Krakaren spawn flood them, and Carl's warnings, accurate but unwelcome, are all that keep the surviving crawlers ahead of the tide. A floor-wide plan comes together with Prepotente and Miriam Dom, working the same idea from the network's other side: blow every ghoul generator simultaneously. At the trainyard the party's god-summoning gambit goes wrong, and Carl ends up caught between a station mimic and the summoned war god Grull; Grull annihilates the mimic, steps on Carl, and is finally driven into the Abyss by the party. With the generators destroyed on schedule, the remaining crawlers escape the floor. Carl and Donut bid farewell to the Nightmare Express crew, Agatha makes a brief reappearance, and Carl leaves the Iron Tangle with a promise: he is going to break the people who run this game.

The book ends with the fourth floor's collapse averted at the last possible hour. Carl's plan works: coordinated with Prepotente and Miriam Dom on the far side of the subway network, the crawlers blow every ghoul generator at once, stopping the undead flood and saving the survivors massed at the exits. Before that, the trainyard battle nearly kills Carl, caught between a station mimic and the summoned war god Grull; Grull destroys the mimic, and Carl's allies drive the god into the Abyss. The party says goodbye to the NPC train crew they befriended, and Agatha, the strange old woman from the first floor, resurfaces briefly. Carl closes the floor with a promise to break the people running the game. In the epilogue, the team learns Zev has been taken away for re-education over her sympathy for the crawlers, replaced by the hostile liaison Loita; on Odette's show Carl publicly confronts Odette over her role in Hekla's story, and a warning about the murderous crawler Chris is censored before it can air. Donut chooses which sector of the fifth floor the party will enter. Katia stands among the top crawlers alive, the Cookbook rides in Carl's inventory with his own additions, and the party descends carrying more fame, more enemies, and the first real seeds of organized resistance.