Sea of Fire (Star Legions: The Ten Thousand Book 5). Star Legions: The Ten Thousand, #5

The elite mercenaries of the Black Legion have fought their way free of the clutches of the Imperial Fleet, but only at the cost of many warriors and ships. The survivors lead their battered ships out to the fringes of the Empire, but every day that passes gives the Emperor time to mobilise ships and soldiers to bring the final blow against the exhausted mercenaries. They must continue on to the Sea of Fire, the deadly border region between Hayastan and the Carduchian Wilderness, or face utter annihilation at the Emperor's hands.
Ancient stories tell of these dead sectors of space, vast ocean of emptiness, with few worlds or moons able to supply the fleet. The border itself is a place so deadly that the fiery storms can lash out and destroy even the strongest of ships, and there are rumours of mysterious and powerful warships infesting the region. Xenophon will have to use every ruse and stratagem he can come up with to give them any possibility of escape.
They might even stand a chance if the leaders of the Legion didn't use every opportunity to enrich their position and turn on each other, even when in the middle of catastrophe. Sea of Fire is the fifth book in the Star Legions series from Michael G. Thomas, the bestselling author of the Star Crusades series. Previously published as the Black Legion series.