The Iscariot Sanction by Mark A. Latham
In an alternate reality, the world is in peril. Young Apollo Lycea agent Lillian Hardwick, and her Majestic partner Sir Arthur Furnivall, are sent to expose a plot to seize power of the Empire. They must overcome supernatural foes and unlock the secret of the Iscariot Sanction to discover a danger unlike anything they have faced before; a threat that will leave them-and the Empire-changed forever.