Probability Moon

Humankind has expanded out into interstellar space using star gates-technological remnants left behind by an ancient, long-vanished race. But the technology comes with a price. Among the stars, humanity encountered the Fallers, a strange alien race bent on nothing short of genocide. It's all-out war, and humanity is losing.
In this fragile situation, a new planet is discovered, inhabited by a pre-industrial race who experience shared reality-they're literally compelled to share the same worldview. A team of human scientists is dispatched-but what they don't know is that their mission of first contact is actually a covert military operation.
For one of the planet's moons is really a huge mysterious artifact of the same origin as the star gates . . . and it just may be the key to winning the war.