Hunter-Killers

The machines were responsible for the creation of hunter-killers, at least if Ignacius is to be believed.
The bogeyman of fiction meeting the horrors of posthuman war, the hunter-killers combine transgenic and synthetic DNA to become something more than any natural creature. They are terrifying and vicious, seeking the extermination of humanity as part of in-bred programming. However, their artificial nature has led to defects and degeneration in the century and change that has passed since the war. The hunter-killers of the present day are mere parodies of the original models created to wage insurgent war against humanity.
Hunter-killers come in a variety of forms, but they are generally divided into three main categorizations that have distinct member subspecies.
Rovers, such as scouts, marauders, and gatherers (each distinct threats in their own right) are capable of operating independently from a hive. These hunter-killers are the main kinds found in the Green Zone, and they are just as prolific in the dust. Even with their autonomy, they are rarely able to wander as far as the Alcoves.
Scouts are small, creeping creatures capable of great bursts of speed. Their claws are able to rend most protective armor and barriers, and their small size makes them able to avoid retaliation for their attacks.
Marauders are grotesque parodies of humanoid forms, created as hunter-killers capable of leading the efforts of others, though not quite as powerful as hive mothers. Barely intelligent, they stalk with malice, launching spines tipped in acid that damage armor and stun their targets. Marauders are known to be keenly intelligent, often hunting humans when they are not consumed by blind rage.
Gatherers walk the line between scouts and marauders. Not quite humanoid, but possessing grasping hands, they search for biological material and are dangerous foes if encountered unprepared–someone who crosses their path is no more than raw materials to the gatherer's mind.
Drones are the subservient hunter-killers that manage many of the tasks of the hive.
Cores are the hunter-killers believed to form the basis of the hives.
The hive mother is the most commonly described core hunter-killer, but their role is often disputed. Although they were originally believed to be responsible for the creation of new drones, later encounters have shown that they may only carry drones into battle with them, and they may function as guardians of the hive. Reports from a dust-lord, forbidden to circulate by Ignacius' second-in-command Tiresias, indicate that there may be "seed" hunter-killers that turn raw biomass into new terrors.