The Hero of Ages

From #1 New York Times bestselling author Brandon Sanderson, the Mistborn series is a heist story of political intrigue and magical, martial-arts action.
Who is the Hero of Ages?
To end the Final Empire and restore freedom, Vin killed the Lord Ruler. But as a result, the Deepness—the lethal form of the ubiquitous mists—is back, along with increasingly heavy ashfalls and ever more powerful earthquakes. Humanity appears to be doomed.
Having escaped death at the climax of The Well of Ascension only by becoming a Mistborn himself, Emperor Elend Venture hopes to find clues left behind by the Lord Ruler that will allow him to save the world. Vin is consumed with guilt at having been tricked into releasing the mystic force known as Ruin from the Well. Ruin wants to end the world, and its near omniscience and ability to warp reality make stopping it seem impossible. She can't even discuss it with Elend lest Ruin learn their plans!
Other Tor books by Brandon Sanderson
The Cosmere

The Stormlight Archive
The Way of Kings
Words of Radiance
Edgedancer (Novella)
Oathbringer
The Mistborn trilogy
Mistborn: The Final Empire
The Well of Ascension
The Hero of Ages
Mistborn: The Wax and Wayne series
Alloy of Law
Shadows of Self
Bands of Mourning
Collection
Arcanum Unbounded
Other Cosmere novels
Elantris
Warbreaker
The Alcatraz vs. the Evil Librarians series
Alcatraz vs. the Evil Librarians
The Scrivener's Bones
The Knights of Crystallia
The Shattered Lens
The Dark Talent
The Rithmatist series
The Rithmatist
Other books by Brandon Sanderson
The Reckoners
Steelheart
Firefight
Calamity