The Final Empire is a world controlled by the Lord Ruler, a powerful and brutal being who has lived for 1,000 years. He is thought to be immortal and is worshiped as a god. The Lord Ruler is a powerful Allomancer. Allomancy is the genetic ability that allows an Allomancer to consume and metabolize (or burn) metals for magical powers, which can enhance the Allomancer’s physical and mental capabilities. An Allomancer who is only able to burn one of the Allomantic metals is known as a Misting. Anyone who is capable of burning all of the Allomantic metals is a Mistborn.
Those who have Allomantic powers passed down through their bloodlines for generations since the Lord Ruler took power are called noblemen. All others without powers are called skaa. They labor as slaves for the noblemen. Skaa have no rights and are property of the Lord Ruler, rented out to noblemen for work. It is illegal for noblemen to have children with skaa for fear that skaa slaves will be Allomancers. Though illegal, half-skaa, half-noble people exist but are hunted. While the skaa are controlled by the noblemen, the noblemen are controlled by Inquisitors and the Canton of Inquisition, the police arm of the Final Empire; and Obligators and the Steel Ministry, the religious and legal arm of land.
Three years earlier, a half-skaa thief and conman named Kelsier, along with his wife, Mare, were caught stealing from the Lord Ruler and sentenced to mine the alloy atium from the Pits of Hathsin, a brutal prison camp. When Mare was beaten to death in the camp, Kelsier snapped and discovered that he was Mistborn, killing the guards and escaping the camp. For years, Kelsier has roamed the plantations in the Final Empire, encouraging the downtrodden skaa slaves to rise up and fight their oppressive government.
Kelsier returns to Luthadel, the largest city in the Final Empire, and rounds up his former thieving crew for a final job: overthrow the Final Empire by stealing its treasury and collapsing the economy. Sixteen-year-old Vin is a street urchin in Luthadel. Realizing that Vin is a half-skaa Mistborn like himself, Kelsier recruits her for his crew and teaches her to develop her Allomantic powers, which include burning pewter to strengthen her body, burning tin to enhance her senses and burning steel to pull and push metal.
Kelsier plans to destroy the Final Empire’s center of government by starting a war within the noble houses, raising and training a skaa army and getting the local Luthadel garrison out of the city. The newly trained skaa will need to invade, steal the Lord Ruler’s hoard of atium — the metal that is the cornerstone of the economy — and kill the Lord Ruler himself, using a mythical 11th metal Kelsier claims he’s found.
Vin’s role in the crew is to assimilate, spy on the nobility and listen to rumors. Sazed, one of the crew, helps Vin learn how to dress, act and speak like a noblewoman. Unlike most of the crew, Sazed isn’t a half-skaa Misting but a Feruchemist. Like Allomancy, Feruchemists draw power from metals, but instead of ingesting them, Feruchemists wear the metals and store abilities such as strength, youth and memories that can be used at a later time.
Sazed teaches Vin to spy on the nobility by attending elaborate balls. She poses as Valette Renoux, a niece to Lord Renoux, a nobleman working with Kelsier's crew. She dances with the young noblemen and shares and spreads gossip among the noble women, gaining information about house wars, which may help her crew.
While attending the parties, Vin meets and falls in love with Elend Venture, heir to House Venture, Luthadel’s most powerful noble house. Twenty-one year-old Elend is defying his father’s and society’s rules. Along with the heirs of other noble houses, he secretly plans to build a better society when they ascend to the head of their own houses.
The crew succeeds in starting a house war by assassinating several powerful nobles and making it appear that the other houses are responsible. The crew’s efforts, though slow, are successful in recruiting 7,000 skaa soldiers to join their army, and these men are sent to caves outside of Luthadel to be trained.
All goes according to plan until the majority of the skaa soldiers are killed. One overconfident member of the crew uses the army to attack an unimportant Final Empire garrison. Kelsier finds out about the attack while it’s in progress. Though he tries to aid them, he is too late.
He orders the remaining soldiers be smuggled into Luthadel and hidden. The only benefit of the unwise attack is that the Luthadel garrison leaves the city to round up stray skaa soldiers. This leaves the city unprotected.
To discourage any additional rebellions, the Lord Ruler has many innocent skaa beheaded in the city square, which only serves to anger Kelsier and his crew. The Lord Ruler’s action steels the rebel’s resolve to bring down the Final Empire.
The house wars prove to be successful, resulting in broken alliances between noble families. This places Luthadel in a state of fear. As house wars intensify, Vin hears of a plot to kill Elend. She saves him, killing a Mistborn assassin in the process.
As the city grows even more chaotic and Inquisitors slaughter skaa crews, Kelsier fears his brother, Marsh, has been caught and killed. Marsh, a Misting, was a part of Kelsier’s crew and had infiltrated the Steel Ministry as an acolyte. In anger and sadness, Kelsier decides to attack the Lord Ruler where he will feel it most: the atium mines in the Pits of Hathsin. Kelsier attacks the mines, and using Allomancy, breaks the crystals that produce the rare metal.
In retaliation for the destruction of the mine, the Lord Ruler rounds up more innocent people to behead in the square. Lord Renoux and his estate are among those captured and sent for execution. Though Kelsier's crew manages to free most of them, Kelsier stands up to the Lord Ruler. In a dramatic confrontation in the city square, the Lord Ruler kills Kelsier.
Though his death would seem to make Kelsier’s plan a failure, the crew realizes that he has become a martyred symbol of hope for Luthadel's skaa population. The skaa react to Kelsier’s death by rising up and overthrowing the city with the help of Kelsier's army.
Before his death, Kelsier had tried to unlock the potential of the 11th metal, which was rumored to be the Lord Ruler's weakness. He was unable to do so and leaves the bit of metal for Vin, asking her in a note to figure it out. Vin takes the 11th metal and goes to the palace to kill the Lord Ruler. She is captured and left in a cell to be tortured. Sazed and Elend come to her rescue. Using Feruchemy, Sazed helps Vin escape the prison, but she does not leave the palace.
Vin attacks the Lord Ruler, and after ingesting the 11th metal, she sees a glimpse of who the Lord Ruler was before he ascended to power and who he would have been had he not. She realizes the Lord Ruler was a Terrisman. She fights the Lord Ruler, who is revealed to be both an incredibly powerful Allomancer and a Feruchemist, the combination of which grants him incredible healing powers and eternal youth.
Vin is almost killed, but with help from Marsh, who wasn’t killed but turned into an Inquisitor, she manages to separate the Lord Ruler from his Feruchemical bracelets, which provide him with constant youth, causing him to age rapidly. The Lord Ruler’s last words to Vin are that by killing him, she has doomed the Final Empire to a greater evil.
Using a spear, Vin stabs the Lord Ruler in the heart, killing him. The Final Empire collapses, but Elend is able to stop the city from falling into complete anarchy by uniting Luthadel under a new system of government.