Praetorian: Blades of Antioch: Book 6

Rome has a new emperor; a strong emperor. Septimius Severus, a lion of the battlefield, now moves east to face the usurper Pescennius Niger, contesting with a clever opponent with the ultimate prize in the balance: the throne of Rome.
But with civil war raging all across the East, problems abound. One of the frumentarii, the emperor's military agents, has gone missing in Arabia, and with him has gone a list of the service's personnel.
With just a slave familiar with the east, Rufinus sets off for an outpost on the edge of the empire, seeking the missing agent in an attempt to save all those on the list before it falls into enemy hands. A war-torn land, treachery and violence await…