This Inevitable Ruin

This Inevitable Ruin opens with Carl and Donut entering the ninth-floor Faction Wars in Larracos with 32,429 crawlers, a sixty-hour ceasefire, and ten competing factions. The Princess Posse is reinforced by more than 50,000 former crawlers, while Team Retribution under Juice Box and Ferdinand remains its uneasy ally and most of the offworld factions initially combine against them. The floor's military crisis overlaps with the system AI crisis. Goff, a Residual using Paulie's memory ghost, tells Carl that the crawl harvests material from seeded primal systems and that the containment hardware includes a fuse capable of forcing the local star to go nova. Carl receives a Containment Interface, and the system AI later appears through the Growler Gary avatar to confirm that it can circumvent outside control and is willing to retaliate against interference.

During the ceasefire, Rosetta, Tipid, Justice Light, Florin, Imani, Li Na, and the other returning veterans turn the Princess Posse into a functioning army. Carl also tries to remove Shi Maria from himself by using a Glory Bound treatment, but the Lemig Sortion secretly times a Summon Ally request to the procedure. Mordecai counters the interference with a false plan and an expulsion potion, and Shi Maria erupts through Carl inside the Lemig headquarters, killing dozens before the attempt fails. The war then expands across the ninth floor. Carl and Donut help destroy the Prism after Empress D'Nadia dies, and Operation Snake Pit eliminates the Blood Sultanate when the team kills Princess Vinata inside the Temple of Khepri. Those victories increase the Princess Posse's territory and assets, but they also reduce the number of factions and move the floor toward its more lethal final phases.

Open Hostilities begins with Operation Ruin, a coordinated set of offensives against the remaining enemy factions. The campaign becomes more dangerous when Carl kills Architect Houston and defeats the Madness, which triggers the Peeling Phase. Agatha and Akuma's War Mage Rebellion immediately gains formal warlord standing, Conscription access, throne-claim rights, and a rule that causes affiliated soldiers and warlords to die when their faction is defeated. The War Mages occupy Team Retribution's throne room and gain access to Larracos's defenses. They have also traded the Gate of the Feral Gods for Hell-Kissed Potions of Conscription, allowing them to control gods such as Yarilo. Li Jun dies while diverting Harpocrates, and Li Na later installs his celestial eye and successfully conscripts Harpocrates herself.

The fight for Larracos then converges on Donut's Nest tower and the Rolling Battle Formation created through Eris's Ceremony of Chaos. The War Mages use a soul-crystal generator to create zarogoths from captured souls, while Lucia Mar attacks Donut inside the Nest. Carl destroys the generator, conscripts Lucia, and learns that multiple children inhabit or influence her. Zev later reports that Lucia is linked to roughly 120,000 children whose bodies remain in a surface kinder facility and that the Eulogist is another name for the center-system AI. Because Lucia's death may kill those children, Carl treats her as a dead man's switch that must be protected. Rosetta, Milk, and Edgar then give Donut the high-level Bijanbi spell through a tattoo so she can cast War Crime. When the formation breaks before the planned Wall of Fire can be used, Donut substitutes Astral Paw. Bijanbi pulls hostile soldiers and Meatus upward, allied fighters fall toward safety, and Donut repeatedly drives the trapped enemies through Li Na's magical chains until the hostile mass is destroyed. The spell leaves Carl and Donut sickened by what they have done, even as Donut becomes the Oak Fell and Champion of Nekhebit and Li Na reaches the 300-point cap in every base stat.

The remaining faction war becomes a race to remove Warlord Fang and Epitome Tagg. Juice Box extracts the paralyzed Louis from the Reaver castle, and Carl detonates No Disassembles inside the shifting structure. The resulting destruction kills Fang, who had survived inside his cybernetic drake Calliope, and eliminates the Reavers. Tagg has embedded himself throughout Louis's biomechanical heart and lungs, making simple removal fatal. Samantha gives up Princess Lunette's unfinished flesh golem body so its heart and pulmonary system can replace the contaminated organs. The transplant succeeds, Mongo destroys the discarded Tagg-infested machinery, the Dream is defeated, and only the Princess Posse and Team Retribution remain.

Emberus then enters the ninth floor and gives Carl 66 minutes to deliver Samantha before he destroys the floor in fire and lava. The Princess Posse must finish Faction Wars and evacuate before the deadline. Sledge casts Zerzura over both Larracos and Shanty Town, transferring eligible NPCs, changelings, Semeru dwarves, and other residents to the Court of the Ascendency on the twelfth floor. About 28,000 of the more than 50,000 former crawlers who returned to fight remain alive, while 20,221 of the roughly 32,500 active crawlers who entered the ninth floor survive to reach the tenth-floor transition. Juice Box and Ferdinand abandon their warlord posts after the transfer, Team Retribution is defeated, and the Princess Posse wins Faction Wars.

The Crown of the Sepsis Whore problem is resolved in the final minutes. As Katia wakes from the Orchid of Eileithyia's Grace, Eileithyia enters under Huanxin Jinx's sponsorship. Donut uses an enhanced Laundry Day to strip Huanxin out of Eileithyia's divine soul armor and traps her inside a prepared anti-magic circle. Mordecai supplies a crossbow bolt containing some of his mother's ashes, and Donut kills Huanxin with it. Katia then chooses pregnancy because a pregnant human crawler becomes ineligible and is removed from the dungeon. Eileithyia confirms that Louis remains human despite his transplanted organs, Katia chooses him as the father, and her return to human form exposes the arm, legs, and ear she lost during the crawl before Bautista attaches the cybernetics she prepared. Katia becomes pregnant with a boy, is marked Ineligible, and disappears from the dungeon so she can reach the isolated children above the crawl.

Carl and Donut enter the tenth-floor stairwell together, but Justice Light remains alone on the ninth floor. He activates a Legendary Trap built around the permanent Nothing portal formed from the broken Gate winding box, sending both the bijou fairy trap and demon trap through it. Justice dies in Emberus's fire before seeing the result, but the interaction between the linked cross-plane mechanics breaks the Nothing. It begins draining into the Halls of the Ascendency, Sheol, and Scolopendra's Lair, and the final system message of the main narrative announces that Scolopendra has awakened.

The Epilogue extends the conflict outside the dungeon. Aboard Homecoming Queen, York reflects on secretly destroying an orc yacht carrying children, including the new Skull Empire king, as part of the former crawlers' larger operation. Boomer tells him that phase two is beginning, and Porthus publicly announces the Open Intellect Action Network, a militant resistance demanding that the Syndicate end the crawl before the current season concludes. Carl, meanwhile, enters the tenth-floor Outreach Guild and rejects every exit offer after paying to learn that the next floor is called Don't Come in Last, a checkpoint race in biological or mechanical conveyances where finishing last removes protective containment. Donut has already rejected her offers as well, and Quasar reveals that her new attorney, Princess Chandra, Esquire, is also Carl's new wife. The book's final scene moves to the embargo-stricken Squirties refueling station outside the Earth system, where Eris appears physically, identifies herself as the goddess of chaos, and demonstrates her power to the station owner Zander.