Tread of Angels - Rebecca Roanhorse - Bog

"Celeste, a card sharp with a need for justice, takes on the role of advocatus diaboli, to defend her sister Mariel, accused of murdering a Virtue, a member of the ruling class ... The year is 1883, and the mining town of Goetia is booming as prospectors from near and far come to mine the powerful new element Divinity from the high mountains of Colorado with the help of the pariahs of society known as the Fallen. The Fallen are the descendants of demonkind living among the Virtues, the winners in an ancient war, with the descendants of both sides choosing to live alongside Abaddon's mountain in this tale of the mythological West"--