Requiem for the Conqueror. Forbidden Borders 1

This rich and exciting sci-fi trilogy follows the search of one man-raised to be the ultimate general, the penultimate killing machine-for his own humanity and for the son he's never known. The final conflict is about to begin....   The Forbidden Borders form a seemingly unassailable gravity-powered barrier, cutting humankind off from the wider universe, confining rival empires to a few star systems, and leaving them to strive endlessly against one another for total control.
But now the weakest have fallen, only two mighty empires remain, and each must once again turn to the man both fear more than they fear one another. The man each is determined to hire-or, failing that, to assassinate-Staffa kar Therma, Lord Commander of the Companions.   Trained to be the ultimate killing machine, the penultimate general, Staffa has led his crack Companion mercenary troops to victory time and again.
Throughout the human worlds, the Lord Commander is cursed as the Star Butcher, bringer of death and destruction. And never before has he turned his back from undertaking a new contract.   But along with his most recent victory has come a discovery that will have repercussions throughout all the star systems within the Forbidden Borders. For Staffa has learned that the son stolen from him in infancy may still be alive, and nothing will stand between Staffa and the search for his son-even though his quest may well lead to his own destruction....