Books like Servant of the Crown

Captain Tamas is an ambitious young officer in the Adran army. As a commoner, he is one of very few without noble blood to hold a rank. When he challenges the son of a duke over an insult, the subsequent duel lands him in hot water with the nobility and the royal cabal of Privileged sorcerers. Tamas is soon drawn into a conflict that goes to the very highest office in the land, and his only ally is the most unlikely of people; a young noblewoman named Erika, who needs Tamas to teach her how to wield her powers as a powder mage. Thirty-five years before the events of Promise of Blood.