Genesis Weapon (The Genesis Project‪)‬

In the third book of the epic science-fiction saga, The Genesis Project, the newly-formed alliance between three peaceful worlds is to come to blows with a seemingly unstoppable adversary…
It began with a single message that said: "I am Toarvak 6, destroyer of worlds, servant of the Kresh. You are not Kresh. Toarvak 7 has been informed. I am the Will and the Way."
The alliance of humans and the Gnathe, a highly-evolved alien species, was besieged by Toarvak 6, a seemingly indestructible spaceship until it was mysteriously and utterly destroyed. Left to piece together their ruined worlds, the alliance begin to uncover what it was that saved them from complete obliteration. But as they attempt to prepare themselves against renewed onslaught by the Kresh with the arrival of Toarvak 7, a new threat comes in the form of a world-infecting parasitic organism called The Goss.
Attacked from all sides, it appears that the alliance will inevitably crumble beneath the weight of insurmountable foes… unless something can save them from annihilation.