Hidden Empire (Saga of Seven Suns)

In our galaxy's distant future, humans are one of three known intelligent races. Having had the ability to navigate star travel for only a few centuries, we are considered "the new kids on the block" in a long-established universe. The second intelligent race is the Ildirans, who are ruled by their Mage-Imperator; and the third race, the Klikiss, seems to have vanished and left behind a world full of artifacts and remarkable technology, which humans are now beginning to find and utilize. One such piece of technology is a device that has the power to turn a gaseous and useless supergiant planet into a small sun, thereby creating a new solar system in which humans can live. But when the device is tried for the first time, it awakens the wrath of a previously unsuspected fourth race, the Hydrogues -- and a galaxy-spanning war that threatens all life begins.