The ashes of worlds - Kevin J. Anderson

The allied factions of humanity, along with the waning Ildiran Empire and the powerful water elementals and sentient trees, have defeated the near-invincible alien race of the hydrogues, driving them back into the depths of gas-giant planets. But before peace can heal the wounds between the races, two ancient enemies return: the capricious fiery elementals, the faeros, who mean to burn all those who fought alongside their mortal enemies. And the lost hive race of the Klikiss, who intend to reclaim all the worlds they inhabited 10,000 years earlier, worlds that are now home to many human colonies. Meanwhile, the leader of the Terran Hanseatic League, Chairman Basil Wenceslas, intends to pull all of humanity's unruly stepchildren into his iron grip - even if it means he has to hold the Ildiran Mage-Imperator hostage, risking renewed war with an entire alien civilization.
THE ASHES OF WORLDS brings to a thrilling conclusion the myriad storylines of galactic warfare and personal betrayals, starlost romances and titanic alien conflicts.