> *Major spoilers through This Inevitable Ruin.*
The relationship between Carl and Katia Grim begins as a temporary protection arrangement on the Third Floor and develops into one of the central family bonds of the crawl. Carl initially sees Katia as an inexperienced crawler whom he and Princess Donut have promised to keep alive. By the Ninth Floor, he treats her as a trusted engineer, battlefield commander, confidante, and member of his family. Katia, in turn, grows from accepting Carl's instructions to challenging his judgment, designing operations with him, and leading forces beyond his direct control.
Their bond is neither romantic partnership nor simple mentorship. Carl's protectiveness helps Katia survive long enough to develop her abilities, but it also produces friction when he mistakes responsibility for control. Katia's loyalty repeatedly supports Carl's larger plans, yet she retains her own party, relationships, private wounds, and eventual purpose. The dungeon exploits that independence by creating situations in which helping Katia appears to endanger Donut. Carl's defining response is to reject the imposed choice: he will not preserve one member of his family by sacrificing another.
The promise on the Third Floor
Carl and Donut meet Katia in Hump Town after Hekla asks them to help her gain experience. Katia is only level nine and visibly uncomfortable with the doppelganger body selected for her by an unhelpful game guide. Although the interface labels her human, she must sculpt her own appearance from available mass, cannot simply command herself to look normal, and experiences pain while reshaping. Her uncertainty, low level, and poorly understood class lead Carl to regard her as a liability. Mordecai nevertheless recognizes the potential of a crawler who can alter her body while preserving equivalent mass.
The initial arrangement is explicitly provisional. Hekla asks Carl and Donut to add Katia to their party, protect her, and help her catch up. Carl worries that shared experience will slow his own progress, while Donut insists that their promise to Hekla matters. Katia does not immediately accompany them into the most dangerous part of the Hump Town quest, but Carl entrusts her with a remote detonator and directs her to activate it if he and Donut die or give the order. The act is practical rather than intimate, yet it establishes a pattern that persists throughout their relationship: Carl gives Katia responsibility before he fully trusts her, and Katia proves dependable under pressure.
That pressure becomes lethal when the failed spell surrounding Remex produces a blast zone and locks the saferooms. Katia cannot enter the Desperado Club because her status as a quest host blocks the escape route available to Carl and Donut. She tells them to leave her and begins directing nearby non-player characters back into their homes. Donut refuses to accept abandoning her, and Carl chooses an improvised attempt to survive the magical blast rather than the safer course of running to the club. After the group reaches the stairwell, Katia uses the detonator on Carl's instructions. Her action helps produce the final release that raises her from level nine to level twenty-one and publicly associates all three crawlers with the result.
By the time they appear together on Odette's program between floors, Katia is introduced as the newest member of Donut's Royal Court. Carl also receives a warning that Hekla may be using Katia's access to gather information and maneuver Donut into Brynhild's Daughters. He does not blame Katia for the possibility. He describes her as harmless, notes that Mordecai likes her, and accepts Odette's judgment that Katia is not knowingly participating in Hekla's plan. The distinction matters later: Carl learns to separate Katia's loyalty from the conduct of people who claim authority over her.
Partnership in the Iron Tangle
On the Fourth Floor, Katia becomes part of Carl and Donut's daily operating unit. Carl helps her experiment with mass, balance, armor, and vehicle forms, while Katia studies the Iron Tangle's routes more closely than either of them. His instruction accelerates her transformation from a frightened support crawler into a powerful physical specialist. It can also be overbearing. When Katia proposes turning herself into the front structure of a rescue train, Carl objects that she will die. She answers that he dislikes the plan partly because it is not his idea and calls him a backseat dungeon driver. Her accusation identifies a real limit in Carl's leadership: he is willing to risk himself on improvised plans but struggles when someone he feels responsible for chooses a comparable risk.
Katia proceeds because rescuing the trapped crawlers is her plan and because Hekla has brought the Daughters back for her. Carl negotiates for Katia to remain in his party through the operation and helps design the protective layers that let her function as the train's cowcatcher. When her health suddenly collapses, Donut discovers that Hekla has fired invisible phased bolts into her. Carl orders Katia to shed her accumulated mass, catches her when she reappears unconscious, pulls the hidden bolts from her body, and uses their descriptions to identify the assassination attempt. His response is focused on stopping the damage rather than retaliating, even after Donut attacks Hekla.
The confrontation changes Katia's relationship with both groups. Hekla and Eva admit that Katia was being used to provoke Carl, while Eva weaponizes Katia's history of rejection and calls her useless. Katia activates Rush against Eva but veers off course and kills Hekla instead. During the ensuing fight, Carl and Donut protect Katia, use Hekla's reanimated body to force the Daughters back, and escape with the rescue train. Carl then defends Katia to the surviving Daughters, explaining that Hekla tried to kill her as part of a larger attempt to isolate Donut. He does not deny the death or pretend Katia is unaffected. When she says that nothing about the situation is acceptable and that she has nowhere to break down, Carl and Donut share an exhausted, involuntary laugh with her before returning to the crisis around them.
The aftermath removes the expectation that Katia will return to Hekla's authority. She remains with Carl and Donut, but no longer as the low-level crawler they are carrying. Her study of the map, expanding control over her body, and willingness to question Carl make her essential to the effort to move survivors through the Tangle. She receives equipment that upgrades Rush to Crowd Blast and gives Carl her former auto-buckler when she can no longer use both items. The exchange reflects their new balance: Carl still helps interpret equipment and tactics, but Katia has become strong enough to improve his loadout and rescue others in her own right.
Engineering and divided command
On the Fifth Floor, Carl and Katia's cooperation is most visible in engineering. They build the Royal Chariot together, discuss using its chassis as the basis for a larger vehicle shaped around Katia's body, and refine designs in the upgraded crafting space. Carl recognizes that she is particularly good at the work. Katia also maps locations, teaches Donut to use unfamiliar equipment, and translates discovered measurements into practical routes. These are not auxiliary tasks: their survival increasingly depends on Carl producing dangerous mechanisms and Katia making them mobile, correctly proportioned, or geographically useful.
The Gate of the Feral Gods makes their complementary skills decisive. Katia interprets the notes attached to the winding box and watches, determines that the displayed times correspond to locations, and begins recording time-and-place combinations. Carl concentrates on how to assemble and deploy the device, while Katia works out how its components can be arranged to open or close a portal without necessarily releasing a creature on the opening side. During the expedition to the Akula, they enter the underwater operation as a paired unit with Tran and Vadim. When the enormous Lusca swallows the submarine, Carl uses Protective Shell to create an immovable obstruction inside the moving creature, while Katia activates their rocket and deploys the giant saw. The result is chaotic rather than clean, but the combined plan kills the city boss and recovers the gate component.
Their increasing reach also requires them to separate. By the Sixth Floor, Katia leads her own party while Carl and Donut conduct operations elsewhere. The division is a sign of trust, not estrangement. Carl relies on Katia's group for parallel objectives and shared intelligence, and she remains part of the coalition that turns the hunters' event against them. The separation also means Carl does not see every danger affecting her. Eva leaves Katia a supply of blitz sticks that feed comforting false memories, and after the Masquerade she places the Crown of the Sepsis Whore on Katia's head. Carl enters the next floor without knowing either problem's full extent.
The crown and the refusal to choose
Katia reveals the crown crisis to Carl during the Eighth Floor's celestial thorn-room battle. She privately instructs him to repair Yemaya's shrine rather than the shrine his immediate allies expect him to choose, explaining that the result is part of the only known route to save both her and Donut. Carl has almost no time to examine the claim. He acts on it because experience has taught him to trust Katia's instincts and character. Once he understands the crown's Ninth Floor condition—that Donut and Katia cannot both descend while the other remains alive—he rejects the premise outright. The strategic problem is severe, but killing or deliberately abandoning Katia is not an acceptable solution to him.
That commitment is tested when Katia's drug use becomes impossible to hide. After she takes several substances in a Desperado Club drug den, Carl finds her ill, disoriented, and undergoing treatment. His first reaction is anger. Her damaged statistics and new vulnerabilities threaten plans on which many people depend, and her addiction recalls his father in a way Carl resents. Mordecai forces him to recognize that the anger comes from fear and unwanted understanding. Carl then asks what each drug has done and supports the effort to cure her. He also refuses Mordecai's cold strategic alternative of stepping back and allowing Katia to destroy herself, even though her death would remove the crown's threat to Donut.
Carl's support is not uniformly gentle. He insists that Katia proceed with their time-sensitive Guild of Suffering job against Astrid despite her debuffs, vomiting, and visible weakness. Bautista and Imani object that the mission can wait, while Carl believes it is their last reliable chance to secure the orchid needed for Katia's escape plan. Katia chooses to go and squeezes Carl's hand before treatment. In the operation, Carl builds the trap network and Katia positions herself as the mobile finisher and body-recovery specialist. The plan changes when Astrid takes an unexpected route, but they adapt inside the club and complete the job. The episode shows both sides of their partnership: Carl will not discard Katia, but his determination to save her can itself demand dangerous action from her.
Shared memory on the Ninth Floor
The most intimate change in the relationship occurs during the treatment meant to confront Katia's Glory Bound addiction and isolate Shi Maria within Carl. Carl and Katia take related preparations on adjacent cots, but physical contact creates an unintended mental connection. Carl's consciousness enters Katia's dream, where the two are literally joined at the hand. He witnesses the memory of Fannar exposing Katia's past addiction and concealed illness during her attempt to adopt Annie, a terminally ill baby. He also sees Katia's final visit with the child and learns why the same memory is simultaneously her deepest trauma and the refuge recreated by the drugs.
Carl regards the access as a violation rather than a discovery to exploit. Within the dream he tells Katia that she did not ruin every person she loved and names their bond directly: they are family. When outside officials later replay fragments of the dream during an adjudication, Carl orders them to stop, objecting that the memory is not theirs to watch. The experience gives him an understanding that ordinary conversation had not achieved. Katia's addiction, fear of abandonment, desire for motherhood, and tendency to blame herself no longer appear to him as disconnected problems; they are parts of the same wound.
During Faction Wars, Carl and Katia operate as leaders within a larger command structure. They help develop the Princess Posse's plans with Donut, Imani, Elle, Mordecai, and their outside allies. Katia is frequently assigned to another front, and Carl notices her absence rather than trying to pull her back under his immediate command. When they reunite for operations, she joins the small group trusted for critical raids and openly participates when the others challenge Carl's habit of managing every simultaneous battle. Their relationship has moved beyond protector and dependent: Katia can disagree with him in the middle of a war without either of them treating dissent as disloyalty.
The crown remains an exploitable weakness. During the warlord council, Princess Vinata offers to remove Carl's “Katia problem” if he gives a sign of assent. Carl gives none and continues pursuing an outcome that does not treat Katia as a disposable obstacle. The working plan instead uses the Orchid of Eileithyia's Grace to remove Katia from the Ninth Floor in a way that also releases Donut from the crown's condition. Carl worries that Huanxin's promised celestial-attendant outcome will place Katia in another dangerous political game, but he continues preparing contingencies rather than choosing between his friends.
Katia's departure
The end of Faction Wars forces the plan into motion earlier than expected. With only minutes remaining before Emberus destroys the floor, Carl orders Katia to consume the orchid even though she has not finished distributing her possessions and the group has not had a proper chance to say goodbye. He takes her hands, touches his forehead to hers, and reminds her that the escape is her own plan. Katia tells Carl and the others that she loves them before the orchid renders her unconscious.
When Eileithyia appears, Carl, Donut, and their allies prevent Huanxin from controlling the choice. Katia selects pregnancy rather than service on the Twelfth Floor or a constitution enhancement. Her purpose is not merely to escape: pregnant crawlers are removed from the dungeon, and Katia intends to reach the children held in the surface facility. She chooses Louis as the human father after the goddess rules out her initial preference. Eileithyia restores Katia's human body, revealing the limbs and ear she had lost and concealed through her doppelganger form; the prosthetics Katia and Bautista prepared allow the group to respond immediately.
Katia disappears from the dungeon as a human, an expectant mother, and an ineligible crawler. For Carl, the departure resolves the crown's forced choice without treating either woman as expendable, but it is not a conventional victory. The separation is abrupt, the surface remains dangerous, and he cannot accompany or protect Katia there. What he can do is help make her choice possible and trust her to act beyond him. That final transfer completes the reversal begun in Hump Town: Carl once kept Katia alive because Hekla asked him to protect her; he ultimately helps her leave because he recognizes her as family and respects the mission she has chosen for herself.