Warbreaker / Brandon Sanderson.

Enhanced descriptions from Syndetics:

From the author of the connected universe of the Cosmere comes the standalone novel from which spring characters who later play roles in the #1 New York Times bestselling Stormlight Archive.

In the world of Warbreaker, each person is born endowed with the power of one Breath--which can be sold and collected by others, then used to Awaken objects and even corpses to do their bidding. A few individuals who die in glory return as gods, with the power of thousands of Breath, but no memory of their mortal lives--and are enthroned in the Court of Gods in Hallandren's capital. To Vivenna and Siri, princesses of Idris, the abuse of Breath and the claim of the Returned to be gods are repugnant blasphemy. But with one princess wed to the God King of their nation's enemies in a bid for peace, the other finds she must rely on Breath-using mercenaries to try to rescue her sister from her monstrous husband.

Lightsong the Bold, a lesser god who doubts his own religion, starts investigating mysterious murders in the Court of Gods and uncovers haunting clues to his own forgotten past. He is one of four gods who controls the army of Awakened Lifeless soldiers, and one faction is inciting an invasion of Idris despite the marriage treaty. Vasher--wielder of the sapient sword Nightblood--works behind the scenes against the declaration of war, but Lightsong's visions of bloodshed prophesy its inevitability. Can the new queen, unaware of her sister's imminent rescue attempt, persuade Lightsong and also somehow get through to the aloof God King--who she has been forbidden to speak to or even look in the eyes--before her homeland is destroyed?

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