Anvil Gate — Karen Traviss

With the Locust Horde apparently destroyed, Jacinto's survivors have begun to rebuild human society on the Locusts' stronghold. Raiding pirate gangs take a toll--but it's nothing that Marcus Fenix and the Gears can't handle. Then the nightmare that they thought they'd left behind begins to stalk them again. Something far worse, something even the Locust dreaded, has emerged to spread across the planet, and not even this remote island haven is beyond its reach. Gears and Stranded must fight side by side to survive their deadliest enemy yet, falling back on the savage tactics of another bloody siege--Anvil Gate.