From its very first pages, you’d have no idea that Katherine Arden’s sweeping historical fantasy is the author’s first novel. And you could be forgiven for expressing your shock (or envy or frustration) when you find out that in fact the wholly absorbing epic, rooted in Russian folklore, steeped in medieval Russian history, in fact began on a private whim.

“I had always loved Russian stories,” Arden says. She spent the year between high school and college living in Moscow; she majored in Russian and French at Middlebury College in Vermont, intending, at the time, to become a diplomat. “I was all about it,” she recalls. But by graduation, she was burnt out, and so she did what one does when facing a personal crossroads: she moved to Hawaii for a couple of months to work on a farm picking macadamia nuts, and, in the process, launched a fiction career. “I got bored,” she tells me by phone from her current home in Vermont. “So I decided to write a book to entertain myself. I didn’t really have the sense, ‘I’m going to write books and publish them and that’s my career.’ It was more just, ‘Can I do it? I’m going to try; it’s going to be fun!’ ”

Reader, she did it. That book became The Bear and the Nightingale. Set in a remote village at the edge of the wilderness during the middle ages, the novel sparked from a single image. “I had an idea for a scene of this family, in the winter, in Russia, next to this big giant oven,” she says. “So I wrote that scene”—it still opens the novel—and then she asked herself what happens next. What happens is the story of Vasilisa, a free spirit who, as her dead mother promised she would, has inherited her grandmother’s otherworldly ability to see what others cannot: Vasya can talk to the family’s horses and counts the household spirits among her friends. But when a charismatic young priest, fanatical in his devotion, arrives in her father’s home and convinces the villagers that the long-accepted spirits are in fact demons to be exorcised, the village begins to crumble, and Vasya finds both herself and her home in grave danger.

“There's this sense of drama and strangeness to Russian fairy tales,” Arden observes, explaining her affinity for them. “There are some very cool female characters—they do things.” Part of the idea with The Bear and the Nightingale was to capture that drama, but anchor it in reality. Or as she puts it: “actual things, actual people, a real life in a real place.” Once the (decidedly un-fantastical) historical realities of  were established, then, Arden says, she let the regional folklore seep in. “It’s fantasy,” she says, “but it’s fantasy that’s rooted in the same place and time as the history. It’s not a random thing I just sort of pulled out of my hat.”

With The Bear and the Nightingale, Arden’s just getting started. The novel in fact is the first in a trilogy, each drawing inspiration from a different Russian tale; the second book is already done, Arden says; now, she’s in the process of drafting the third. Her process has evolved since she was on that farm in Hawaii. The prospect of dialogue is no longer terrifying. (“I was like, ‘But what would they say? I have to make them say things, right?’ ” she jokes.) In other ways, though, her process looks more or less same. She’s still a great proponent of what she calls the “throw-mud-at-the-wall-and-see-what-sticks approach.” Maybe she does plan a little more now. “But not that much. The most interesting moments still happen spontaneously.”

Rachel Sugar is a writer living in New York.