Soldier of the Legion (Beta 3 Series, 1)

A rough truce divides the known galaxy between the System, the despotic slave empire that rules the inner systems, and the Confederation of Free Worlds. A ConFree unit is dispatched to defend a remote world from a mysterious Systie incursion. Our hero, call-sign "Thinker," will soon discover that giant exosegs, slavers and Systies are just the beginning. Once before the Legion faced the godlike, utterly alien and evil, Omnis, and drove them back at the cost of billions of lives. The future of humanity, all humanity - even the corrupt and decaying System empire, will soon be in the hands of Soldiers of the Legion.