In Her Name: The Last War Series by Michael R. Hicks

Terran survey ship Aurora finds two habitable planets in an uncharted star system. But Aurora is disabled by gigantic alien warships and boarded by blue-skin females with fangs and claws. The warriors slaughter the crew in ritual one-on-one combat. The sole survivor is returned to Earth. This Messenger bears a real-time globe device that counts down to an impending attack. That is the way of the Kreelan Empire. For centuries before man have they waged war, seeking a prophesied savior... moreTerran survey ship Aurora finds two habitable planets in an uncharted star system. But Aurora is disabled by gigantic alien warships and boarded by blue-skin females with fangs and claws. The warriors slaughter the crew in ritual one-on-one combat. The sole survivor is returned to Earth. This Messenger bears a real-time globe device that counts down to an impending attack. That is the way of the Kreelan Empire. For centuries before man have they waged war, seeking a prophesied savior. Soon to be extinct, the ancient species wages their last war, hoping for redemption of sins long past. less