“Let Us Descend,” the title of Jesmyn Ward’s overwhelming new novel, alludes to Dante’s “Inferno,” but her story tells the tale of a real hell on Earth. In one sense, that’s long been Ward’s setting. In “Salvage the Bones,” which won a National Book Award in 2011, she described a poor Black family in Mississippi devastated by Hurricane Katrina. In “Sing, Unburied, Sing,” which won another National Book Award in 2017, she described the notorious Parchman Farm, where Southern slavery was effectively re-legalized for the 20th century.

Now, Ward has moved further back in time to focus on the United States’ original sin, the peculiar institution that managed to reify every circle of Dante’s “Inferno.” Here, in “Let Us Descend,” are enslaved Black women close enough to the birth of America to have heard directly about the horrors of the Middle Passage and even the nature of life on the African continent.

And yet, for all its boundless suffering, this is a novel of triumph.

It begins, appropriately, with battle training. Young Annis, who narrates the story in an urgent hush, is the daughter of her White enslaver and her enslaved mother. Once a month, at night, when their labor is finally done, Annis and her mother practice fighting with spears in the woods. “You the granddaughter of a woman warrior,” her mother tells her. Mama Aza was married to an African king, whose wives served as his guards and hunters. “This our secret,” her mother whispers. “Teaching Mama Aza’s way of fighting, her stories — it’s a way to recall another world. Another way of living. It wasn’t a perfect world, but it wasn’t so wrong as this one.”

Just how wrong becomes immediately apparent.

Hoping to get unfettered access to Annis, her “sire” sells off her mother and moves the girl into his house as a servant. But he soon sells off Annis, too, which begins a descent of unimaginable suffering. Her march to New Orleans — hundreds of miles while roped together with other men and women, in all kinds of weather, with little to eat — is the most grueling and exhausting ordeal Ward has ever described. “We are livestock,” Annis says. “We are expected to walk and drop filth like horses.”

This nightmare makes plain that slavery was not merely a matter of brutal economics. There could be no rational financial reason to starve, drown and cripple one’s valuable livestock. This was fundamentally a system of degradation in the service of White supremacy, which is why certain segments of contemporary society continue to insist that our history remain shrouded in genteel mythology. Ward blasts all that away with the furnace of her prose. In her descriptions of kidnapping, rape, torture and murder, readers will have trouble discerning the job training benefits of slavery that Florida Gov. Ron DeSantis (R) has been nattering on about. But anyone honest enough to consider the most grotesque elements of America’s foundation will find in these pages a relentless exploration of the misery that millions of people endured.

Even as the physical reality grows shockingly clear in “Let Us Descend,” Ward also imagines the spiritual terrain that enslaved Americans may have traversed. During the long, deadly march to New Orleans, Annis begins to sense a presence following her in the dark woods. In one of the novel’s many spectacularly dreamy moments, a troubled spirit that has taken her grandmother’s name suddenly appears in human form:

“The woman stops a tall man’s length away from me, near enough for me to see the black sheen of her eyes, to see that there is something wrong with her skirt, with her top. What I took for silver thread woven into the fabric, glinting in the firelight, is electric, lightning slithering over her garments. Her skirts are not silk, not cotton spun fine, but are obscure and full as high summer clouds, towering in the sky, boiling toward breaking. What I thought was a cape is tendrils of fog draped over her shoulders, yielding curtains of rain down her arms.”

From this point on, “Let Us Descend” moves along two tracks, corporeal and incorporeal. While Annis continues with her fellow prisoners toward New Orleans, she becomes increasingly engaged with the “storm-borne spirit” who wears Mama Aza’s face. But this is no sweet guardian angel; nor is it alone in the spectral realm. As Annis arrives in New Orleans and endures the humiliations of the market and another horrific owner, she finds herself continually negotiating with Aza and other spirits competing for her devotion. Some of them are ominous; a few seem downright insidious.

The nature of this place “sopping with spirit” is not always clear to Annis — or to us — but Ward uses these otherworldly voices to imagine a kind of fluid theology of early Black Americans at a time when their lives were uncontaminated with Christianity and still trailing the clouds of their African ancestors. In her own way, without any formal religious training, Annis struggles with the question of theodicy, trying to understand why no greater power has intervened to stop their suffering. “Why you didn’t spare my mama?” she asks the wind. “Why not me? You could take us out of this place. ... You could have done more.”

Such pained questions — no easier to answer now than then — greatly expand the scope and power of this perilous story told in richly poetic language.