Several years ago, N. K. Jemisin, the fantasy and science-fiction author, had a dream that shook her. In her sleep, she found herself standing in a surreal tableau with a massif floating in the distance. “It was a chunk of rock shaped like a volcanic cone—a cone-shaped smoking mountain,” she recalled. Standing before the formation was a black woman in her mid-forties, with dreadlocks, who appeared to be holding the volcano aloft with her mind. She was glaring down at Jemisin and radiating anger. Jemisin did not know how she had triggered the woman’s fury, but she believed that, if she did not ameliorate it quickly, the woman would hurl the smoldering massif at her.

Jemisin awoke in a sweat and jotted down what she had seen. “I need to know how that person became who she is—a woman so angry that she was willing to move mountains,” she told me. “She was angry in a slow burn, with the kind of anger that is righteous, enough to change a planet. That’s a person who has been through so much shit that she has been pushed into becoming a leader. That’s an M.L.K. I needed to build a world that would explain her.”

Jemisin’s writing process often begins with dreams: imagery vivid enough to hang on into wakefulness. She does not so much mine them for insight as treat them as portals to hidden worlds. Her tendency is to interrogate what she sees with if/then questions, until her field of vision widens enough for her to glimpse a landscape that can hold a narrative. The inspiration for her début novel, “The Hundred Thousand Kingdoms” (2010), was a dream vision of two gods. One had dark-as-night hair that contained a starry cosmos of infinite depth; the other, in a child’s body, manipulated planets like toys. From these images, Jemisin spun out a four-hundred-page story about an empire that enslaves its deities. The book established her as a prominent new voice.

Jemisin is black, in her mid-forties, and wears her hair in dreadlocks. In her author photo, she gazes sternly at the camera, as if ready for literary combat. In person, she is much warmer, but she likes the picture. Typically, at the center of her fiction, there is a character with coiled strength. Jemisin, who has a degree in psychology, is interested in power and in systems of subjugation. In her books, the oppressed often possess an enormous capacity for agency—a supernatural ability, even, that their oppressors lack—but they exist in a society that has been engineered to hold them down. Eventually, the world is reordered, often with a cataclysm.

The notes that Jemisin jotted down after her dream went into a folder on her computer where she stores “snippets, ideas, random thoughts.” Some are drawn from her reading of nonfiction: Jared Diamond’s “Collapse,” Charles Mann’s “1491,” Alan Weisman’s “The World Without Us.” Eventually, she told me, “this fragment pairs up with that fragment, and they form a Voltron, and become a story.” (Voltron is an anime “super robot” that emerges when other machines combine—an artifact of eighties television that Jemisin enjoyed as a girl.)

Another file in the folder was from 2009, when Jemisin attended a NASA-funded workshop, called Launchpad, where participants discussed what Earth might be like if it lost its moon. Some speculated that our planet’s axis would tilt wildly, triggering haphazard ice ages, and that its core might lose its stability, causing earthquakes and volcanic eruptions. The fragments in Jemisin’s folder began to pair up. She imagined a planet that had lost its moon and become seismically hyperactive. Such a place, she reasoned, could sustain life, but just barely; mass extinctions would be common. If the woman in her dream inhabited that planet, she wondered, then what would her civilization look like?

J. R. R. Tolkien once argued that the creation of an imaginary world was the highest form of artistic expression, but that it was also easily undervalued. If it is done well, much of the labor remains off the page. Before Tolkien wrote “The Lord of the Rings,” he invented a mythology, a history, and even languages for Middle-earth; he explained to a friend, “I wisely started with a map, and made the story fit (generally with meticulous care for distances). The other way about lands one in confusions and impossibilities.” It annoyed him that people “stupidly and even maliciously confound Fantasy with Dreaming, in which there is no Art.” He wrote about elves. He wanted to be taken seriously, too.

Jemisin has no interest in pseudo-medieval Europe, but Tolkien would have recognized her rigor. To get a firsthand feel for volcanoes, she flew to Hawaii to smell sulfur and ash. To learn how people prepared for environmental stress, she researched end-of-days survivalists, though she stopped short of going into the wilderness to meet them. (“I wasn’t stupid,” she told me.)

As the idea of an ever-shattering planet developed in her imagination, Jemisin drew a map of a Pangaea-like supercontinent, which she wryly called the Stillness. She reasoned that its wealth would be concentrated in an urban center near the equator, at a geological spot that seemed stable, based on fault lines that she had sketched out. She decided arbitrarily that the woman in her dream lived in the volatile hinterlands—and then began to treat that decision like a discovered fact. “I’m, like, O.K., why isn’t she working to stabilize this powerful, wealthy part of society?” Jemisin told me. “Well, she must have at one point been part of that life, but somehow got away.” Gradually, the contours of a story emerged. “You let intuition do whatever it is going to do,” she said. “I had a sentence in mind: ‘Let’s start with the end of the world.’ That can mean the literal end of the world, it can mean the end of a civilization, or it can mean grief. That was the point where I decided that her son had died.” The grief she understood. Jemisin’s mother had become ill, and would not survive the decade.

After immersing herself in the Stillness for four years, Jemisin finished “The Fifth Season.” The story defied easy literary categorization. It was sweeping but intimate, multilayered but simply told. It could be read as an environmental parable, or as a study of repression, or as a meditation on race, or as a mother’s post-apocalyptic quest. Jemisin wove in magical elements, but she systematized them so thoroughly that they felt like scientific principles—laws of an alternative nature. She evoked advanced technology, but made it so esoteric that it seemed like magic. (Most of her imagined machines were made of crystal. At some point, the inhabitants of the Stillness eschewed metallurgy; the word “rust” even became an expletive.)

She took stylistic chances, too. “The Fifth Season” at first appears to weave together the stories of three people, but late in the book Jemisin reveals that she has merely shattered her protagonist’s story into three narratives, a formal echo of her broken world. The protagonist is an “orogene”—a term that Jemisin derived from scientific nomenclature for a mountain-forming process—who can channel energies that quell or create earthquakes, with varying degrees of control. For the dominant civilization, which enslaves the orogenes—for use as weaponry or as geological instruments—they are a reviled but necessary underclass. The protagonist’s primary narrative blisters with rage and trauma. Jemisin wrote it in the second person, the voice belonging to a narrator who is not revealed until a later book. “I tried her voice in different forms,” she told me. “I couldn’t get too close to her—she was angry with me in the dream, she’s not going to talk to me. That doesn’t make sense, I know.”