Verdant - Achillios Chronicles, #3

Taryn has come a long way in just a few months, and now everything is coming to a head. With the rogue AI Tremayne offline, Taryn and his fellow Servants of the Tower, along with their former enemies from Onyx, must face the ultimate threat to their very existence: a race of aliens who harvest humans for food. The inhabitants of Achillios must come to grips with the fact that their entire world was created to be a trap for these aliens, and they themselves are the bait.
Assisted by the AI of their original colony ship, Taryn and his companions must fully master the ancient technologies left to them, eliminate the alien attackers, and save their world.