The Death of Dulgath - Michael J Sullivan

Three times they tried to kill her. Then a professional was hired. So was Riyria. When the last member of the oldest noble family in Avryn is targeted for assassination, Riyria's Royce and Hadrian are hired to foil the plot. Three years have passed since Hadrian, the war-weary mercenary, and Royce, the cynical ex-assassin, joined forces to become rogues-for-hire. All has gone well until they're asked to help prevent a murder. Now they must venture into an ancient corner of the world to save a mysterious woman who knows more about Royce than is safe and cares less about herself than is sane.