The Leopard Sword: Empire IV by Anthony Riches
Britannia has been subdued - and an epic new chapter in Marcus Valerius Aquila's life begins.
The murderous Roman agents who nearly captured Marcus have been defeated by his friends. But in order to protect those very friends from the wrath of the emperor, he must leave the province which has been giving him shelter. As Marcus Tribulus Corvus, centurion of the second Tungrian auxiliary cohort, he leads his men from Hadrian's Wall to the Tungrians' original home in Germania Inferior.
There he finds a very different world from the turbulent British frontier - but one with its own dangers. Tungrorum, the centre of a once-prosperous farming province, a city already brought low by the ravages of the eastern plague that has swept through the empire, is now threatened by an outbreak of brutally violent robbery. A bandit chieftain called Obduro, his identity always hidden behind an iron cavalry helmet, is robbing and killing with impunity.
His sword - sharper, stronger and more deadly than any known to the Roman army - is the lethal symbol of his unstoppable power. And now he has moved beyond mere theft and threatens to destabilize the whole northern frontier of the empire . . .