Kingfisher subverts conventional definitions of monstrosity through the Wholeness and its fragments and the human characters’ responses to inhuman sentience. Because the narrative is filtered through Easton, who has undergone multiple traumas, the narrative initially interprets the supernatural presence in the mine as dangerous just as Easton does, suggesting that their expectation of monstrosity encourages catastrophic thinking.

The Wholeness challenges human-centered definitions of personhood at a biological level. Despite its sentience and massive size, the Wholeness does not pursue expansion into human society, nor does it display any hostility. When confronted with humans, it uses its self-defense mechanism of imitation. Fragment explains, “IT IS PROTECTION> IF A SHARK COMES, THE WHOLENESS LOOKS LIKE A LARGER SHARK SO THAT IT WILL NOT BE FOOD. EVEN DREAMING, THE WHOLENESS PROTECTS ITSELF” (156). The threat the human characters attribute to the Wholeness arises from uncertainty rather than the Wholeness’s intention or ability to do them harm.

Thunder, who is eventually revealed as the Sentry who had been sent out long ago and never returned, represents the impacts of isolation. It refuses reintegration and kills beyond what is necessary for survival, taking the bones of its victims to construct weapons and a skeletal structure and using the excess food to grow its size. Ingold sheds light on the Sentry’s motivations, observing: “anything that helps the hurt, even healing, feels like it’s trying to strip part of them away” (152). The narrative implies that isolation has reshaped the Sentry’s identity, driving it to desperate violence, which complicates the Sentry’s role as an antagonist, as he sits at the intersection of violent monstrosity and isolated personhood.

Kingfisher’s thematic exploration reaches its climax in Denton’s attempt to kill Fragment and the remaining Sentry. Denton frames the act as necessary for restoring stability, snapping at Easton that “I never thought you’d balk at doing what was necessary” (148). His final plea, as the others prevent him from committing murder, reveals his impulse is rooted in fear and desperation: We could stop it and just go home” (149). In this moment, Denton nearly does something monstrous. Although human, his willingness to kill Fragment further destabilizes the boundary between monster and person. The scene demonstrates that fear, rather than biology, can push an individual toward immoral action.

However, the boundary shifts again for Denton when Fragment helps save Easton’s life. During the rescue, Denton works alongside Fragment and is impressed by his dedication to saving Easton’s life. Later, Denton reveals he feels jealous of Fragment’s medical abilities, noting “‘Fragment’s potentially a better surgeon than I’ll ever be […] Every time I see a patient that could be saved if I could do what he did […] Pretty sure that’ll haunt me to the grave” (170). This shift in perception underscores how direct cooperation alters Denton’s understanding of monstrosity, learning to view Fragment as his medical equal.

Throughout What Stalks the Deep, Kingfisher’s characterization and world-building present monstrosity as both fluid and relational as opposed to a biological reality. Thunder’s violence arises from isolation, encouraging readers to question whether he is a monster or a victim. Fragment and the Wholeness’s benign presentation counters the assumption that personhood is specific to humans, while Denton’s lapse in moral judgment suggests everyone is capable of monstrous acts. In the end, Kingfisher demonstrates the idea that personhood is defined by choice, not biology.

Kingfisher portrays extractive industry—business that remove non-renewable raw materials such as metal, minerals, oil, and natural gas from the earth—as an exploitative practice that harms both humans and the wider environment. The author first introduces the theme as Easton travels to Hollow Elk Mine and documents the harsh contrast between the natural beauty of the area and the mining valleys, where “everything would be stripped away” and “scarred with tracks and great scaffolds of machinery” (27). The machinery that keeps miners from “suffocating or drowning or both” emphasizes the danger involved in the mining industry. However, the nearby “ramshackle little town” (27), which is sustained by “sheer willpower” links the environmental damage to economic instability.

The theme intensifies as the group reaches the abandoned Hollow Elk Mine. The surrounding buildings are remnants of a once-active site, reflecting abandonment after the profitability of the mine declined. A similar image appears in the collection of shacks in Flatwood—the “remains of a company town from another failed mining venture […] everything of use to the company had been stripped out” (47). The description emphasizes an economic withdrawal that has left the community with environmental instability and limited resources. These images reflect the tendency for capitalist industries to prioritize profit over people. However, the personification of the shacks, which “leaned together at odd angles, as if for warmth” (47), strengthens this concept while adding a note of optimism, suggesting communities can support each other in the absence of institutional support.

Roger’s circumstances illustrate the personal dimensions of institutional neglect and industrial exploitation. He is illiterate, and his lack of employment following Oscar’s death, as well as his shack in the neglected area of Flatwood, suggest that he is economically vulnerable and had depended on Oscar for stability. After Oscar disappears, Roger self-medicates with alcohol and relies heavily on Thunder for protection and companionship—"Best damn watchdog in the state” (52). When Thunder’s true identity as the Sentry is revealed and Oscar is confirmed dead, Roger loses his primary sources of both income and companionship. His condition demonstrates how extractive industry combines with personal trauma to create unstable living conditions.

Elijah, in contrast, represents a stabilizing presence within the damaged environment. When the group enters the neglected settlement outside Flatwood, he positions himself as an informal guardian of the community. When he questions Easton and the others, his inquiries reflect a community accustomed to economic instability and outside intervention. Elijah’s authority is relational; he watches over his neighbors and responds when crises arise. Near the end of the novella, Elijah agrees to help Roger monitor the mine, assuming additional responsibility to help keep his community safe. His presence illustrates how individuals are often left to compensate for the consequences of extractive industry.

Roger’s arc reinforces the emphasis on community as a stabilizing force against exploitation. With Elijah’s protection and Ingold’s promise to send books, Roger finds a new support network. His decision to guard the mine with Elijah reflects growing autonomy. The contrast between exploitation and connection conveys that resilience relies on community, not just infrastructure.