Heavily armored Reaver cyborg mercenaries, all machine and armor with no NPCs among them, deployed to breach Carl's castle.
When the Doggie Door beachhead opens below the barracks hill, nearly every enemy soldier that pours out is a Reaver Security Force Cyborg Drop Trooper — not the true Reavers but mercs normally in their employ, and unlike every other force the crawlers have fought, there are no NPCs among them at all. Carl reads them as "space marines": dinged, dirty olive-colored armor mixed with cybernetic enhancements, massive rifles, and not all of them with human-like heads. They sit somewhere between the fully robotic Reavers, who keep a scrap of biological brain inside a shapeshifting nanobot shell, and the softer Nebulars.
The AI explains they are voluntary conscripts trading their biological bodies for Reaver Citizenship, and that these particular troopers belong to Warlord Fang's personal defense deployment — veterans of evicting settlers off Reaver land leases, and thus far more battle-hardened than any crawler. It also notes they are only wearing the "light" version of their kit; had they been allowed their Cronus-class Power Armor, the crawl would already be over. They form a semicircle of One Way Shields and heavy guns, trade smoke bombs with the defenders, and are wiped out to the last when Carl's Tripper sets off their own Explosive Satchels.
Bulky armored androids in scratched, filthy olive-drab plate laced with cybernetics, hefting oversized rifles; many heads are not remotely human.
The Reaver mercenary shock force that establishes and then loses the beachhead below Carl's castle.