The third installment in the Wax and Wayne series, set in the Mistborn universe on the world of Scadrial, this novel follows nobleman-turned-lawman Waxillium Ladrian as he pursues a shadowy conspiracy and a legendary artifact said to grant godlike powers. The story takes place in an industrializing society where some individuals possess Allomancy, which allows them to burn ingested metals for effects like Pushing on metal objects, and Feruchemy, which allows them to store attributes such as weight or health in metal devices called metalminds for later use. Wax is a Twinborn, possessing one ability from each system: He can Push on metals and store physical weight.
A prologue set 28 years earlier establishes Wax's origins. As a 15-year-old in the Terris Village, a peaceful community, he discovers a fellow youth torturing a kidnapped child. When the youth attacks him with Allomancy and throws him from a window, Wax survives by instinctively Pushing on a bullet in his pocket, returns, and kills his attacker, telling the horrified elders he will find his own way.
In the present day, Wax prepares to marry Steris Harms, a noblewoman he initially courted for political advantage but has grown fond of. Wayne, Wax's loyal but impulsive partner, sabotages the ceremony by collapsing a water tower onto the church, believing Wax is not ready. Before the ceremony, a kandra named VenDell asks Wax for help. Kandra are shape-shifting immortal servants of the god Harmony, and VenDell explains that a fellow kandra named ReLuur spent centuries searching for the Bands of Mourning, metalminds allegedly created by the long-dead Lord Ruler that could grant all Allomantic and Feruchemical abilities. ReLuur returned with photographs of a temple but was ambushed in New Seran, losing one of his two Hemalurgic spikes (metal spikes that grant kandra their sapience) and his sanity.
Wax refuses, still furious at the kandra for a manipulation that led to the death of his first wife, Lessie. But when VenDell shows a photograph of Wax's sister, Telsin, apparently held captive in New Seran, Wax agrees. The photograph suggests their uncle Edwarn Ladrian, known as Mister Suit and the leader of a secretive organization called the Set, is responsible. Marasi Colms, a constable and capable investigative partner, takes on the mission to find the spike. Wayne, the kandra MeLaan, and Steris round out the group.
During the train journey, bandits attack in what Wax suspects is a staged robbery. A man with a cane uses a small metal cube to drain Wax's Allomantic reserves. Steris saves Wax by firing a shotgun at an attacker, but the recoil sends her off a bridge; Wax leaps after her and catches her midfall. Marasi recovers the cube.
In New Seran, Wax and Steris attend a reception hosted by Lady Kelesina Shores, a Set affiliate. A beggar outside gives Wax a mysterious coin bearing unknown symbols, which Wax uses to confront Kelesina. He overhears her speaking with Suit through a voice-telegraph: The train robbery was a distraction, and Suit mentions a "second site." Kelesina's steward murders her on Suit's orders, and a planted witness accuses Wax. MeLaan helps him fight off a kill squad armed with aluminum weapons, which resist Allomantic Pushing, and Wax and Steris escape through the roof.
Meanwhile, Marasi and Wayne trace the spike through forensic accounting and graveyard records. After surviving an ambush, Wayne impersonates Death to terrify a middleman into revealing the spike was sent to Dulsing, a settlement northeast of New Seran. The group flees the city.
At a rest stop, Marasi discovers the metal cube does not steal Allomancy but projects it outward; Wax names it an Allomantic grenade. The group confirms that a gold bracelet Wax recovered is an unkeyed metalmind: Normally, a quality called Identity restricts each metalmind to its creator, but this device bypasses that restriction, allowing any Feruchemist who can store health to tap its healing.
At Dulsing, they infiltrate a warehouse concealing a crashed flying vessel from a southern civilization. Marasi and MeLaan locate the study of Irich, the Set's lead researcher, where MeLaan cracks a safe containing the spike, the grenade, and coin-like medallions. Marasi discovers evidence of torture and frees a surviving crew member, a young masked man named Allik Neverfar. Wayne lures guards away so Wax can reach Telsin. A firefight erupts, and the group escapes in a detachable skimmer within the ship, using weight-reducing medallions and Wax's Pushing to launch skyward.
Allik, a Malwish pilot from the far south, explains that when Harmony remade the world, the southern lands froze. A figure called the Sovereign, whom the group identifies as the Lord Ruler, saved the southern peoples by teaching them medallion technology. The Sovereign also created the Bands of Mourning, a device containing all 32 Allomantic and Feruchemical abilities, and hid them in a mountain temple. Telsin urges Wax to fly there before Suit arrives on foot.
At the frozen temple, fronted by a statue of the Lord Ruler holding an aluminum spear, MeLaan absorbs deadly traps as the group advances. Suit arrives with soldiers and opens a sealed door. Behind it, an empty pedestal with a shattered glass case suggests the Bands are gone. Telsin reveals herself as "Sequence," a Set operative outranking Suit, and shoots Wax with an aluminum gun. MeLaan's spikes are removed, reducing her to a mistwraith, the mindless form a kandra reverts to without its spikes. Wax falls through a pit trap. Marasi, Steris, and Allik are captured.
In the catacombs, Wax finds the real resting place of the Bands: a pedestal surrounded by frozen guardian corpses. Suit follows but finds only drained decoy bracers. Pinned beneath rubble, Wax dies. His spirit meets Harmony, who offers a choice between freedom and returning to life. Above, Marasi realizes the true Bands were hidden in the temple's statue: Its oversized spearhead is crafted from 16 interwoven metals. Wayne had broken it off and swapped it into her purse. Marasi taps the Bands, gains all abilities, and flies to Wax, pressing them into his hand. Hearing her voice, Wax chooses duty over freedom, returns to life, and heals completely.
Wax erupts from the temple, sweeps aside soldiers, and Pulls the Set's commandeered airship from the sky. Suit has armed a bomb and proposes a duel with aluminum guns and no Allomancy. Wax drops the Bands overboard as agreed, then tackles Suit instead of drawing, crashing them through the hull. He increases his weight to survive the fall and knocks Suit unconscious. Wayne shoots Telsin, knowing she can heal through her metalminds, and recovers MeLaan's spikes to restore her consciousness. Telsin escapes in the skimmer.
Steris brokers a compromise with Jordis, the Malwish captain: The southerners keep their ship, and the Bands go to the kandra as impartial guardians, in exchange for future trade. Back in Elendel, Wax leads Steris to a penthouse where a priest waits and asks her to marry him out of genuine love. She accepts.
In the epilogue, Suit is visited in prison by a red-eyed creature serving Trell, an unknown god whose forces intend to destroy all life on Scadrial. The creature detonates an explosive, killing Suit. Wax examines the beggar's coin and realizes it is a coppermind, a Feruchemical device storing a memory. He taps it and experiences a vision of a figure with one spiked eye walking through a freezing southern village, kneeling beside an elder woman, and whispering: "Survive."