Revenge of the Damned (Sten #5‪)‬

Sten fully expected to die in a blaze of glory, taking his Emperor's greatest foe with him. Instead, he is a slave laborer in a POW camp deep in the heart of enemy territory. But sitting out the action had never been Sten's style. And now that the war is building to a climax, the Eternal Emperor needs him more than ever. Not even the toughest prison in the known universe can keep Sten from his mission...