The Silverblood promise / James Logan.

Lukan Gardova is a cardsharp, academy dropout, and - thanks to a duel that ended badly - the disgraced heir to an ancient noble house. His life consists of cheap wine, rigged card games and wondering how he might win back the life he threw away. When Lukan discovers that his estranged father has been murdered in strange circumstances, he finds fresh purpose. Deprived of his chance to make amends for his mistakes, he vows to unravel the mystery behind his father's death. His search for answers leads him to Saphrona, fabled city of merchant princes, where anything can be bought if one has the coin. Lukan only seeks the truth, but instead he finds danger and secrets in every shadow. For in Saphrona, everything has a price - and the price of truth is the deadliest of all.