Aliens: Non-Sapient Creatures (Codex)
 Primary Codex Entries
After the geth secure a location, they round up and impale dead and living bodies on mechanical spikes. The spikes rapidly transform these victims into withered husks, extracting water and trace minerals and replacing them with cybernetics.
The cybernetics re-animate the lifeless flesh and tissue, transforming the bodies into mindless killing machines. Some Alliance soldiers refer to the husk-generating spikes as Dragon's Teeth, a reference to the mythological berserkers who sprang up from the earth wherever the teeth of the dragon Ares were planted.
Dragon's Teeth and husks bear little resemblance to other pieces of geth technology. No one is sure why a synthetic race would bother to drain the miniscule amount of recoverable resources from organic corpses, though the value of reusing them as shock troops is obvious.
 Husk: Scions
Though the exact fate of species captured by the Collectors is unclear, the humaniond appearance of the scions gives ghastly clues. The scion's frame and skull are similar to those of a human or asari, but the bone structure is overlaid with a metallic resin. Posthumous examination of their bodies reveals a skin tone resembling that of Reaper husks, but their transformation process seems more extensive. Like husks, they are cybernetically modified on a nano-scale so they can operate even in hard vacuum. Hoses rather thin veins and muscle tissue join major portions of the body together. One arm is replace with a construct that fits a large rifle, turning the creature into a humaniod weapons platform, and a fleshy sack is supported by the creature's back and head.
These sacks contain brain matter and spinal tissue, too much to have come from just one victim. This indicates scions are an amalgam of several individuals, with one primary victim providing the frame and several "secondaries" providing the flesh for a decentralized semi-mechanical nervous system. This decentralization makes them highly resistant to gunshot wounds; even a headshot is not a certain kill.
The scions' weapons, however, indicate that scions retain some living tissue, or at least sustain some of the same electrochemical reactions as those of a human biotic. The weapon creates a powerful warp effect, which is consistent with the eezo nodules visible in the scion's expansive nervous system. Given the rarity of human biotics, it seems likely that these dust-form eezo nodules are deposited during their transformation, rather than requiring a biotic victim in the first place.
 Thresher Maws
Thresher maws are subterranean carnivores that spend their entire lives eating or searching for something to eat. Threshers reproduce via spores that lie dormant for millennia, yet are robust enough to survive prolonged periods in deep space and atmospheric re-entry. As a result, thresher spores appear on many worlds, spread by previous generations of space travelers.
The body of a thresher never entirely leaves the ground; only the head and tentacles erupt from the earth to attack. In addition to physical attacks, threshers have the ability to project toxic chemicals and emit bursts of infrasound as a shockwave weapon.
The Alliance first encountered threshers on the colony Akuze in 2177. After contact was lost with the pioneer team, marine units were deployed to investigate. The shore parties were set upon by hungry threshers, and nearly the entire assault force was killed. Alliance forces recommend engaging threshers with vehicle-mounted heavy weapons.
Varren are omnivores with a preference for living prey. Originally native to the krogan homeworld of Tuchanka, they are, like most life from Tuchanka, savage, clannish, and consummate survivors. They are pack hunters when vulnerable prey is readily available and become scavengers when outnumbered or outclassed.
Their supreme adaptability, vicious demeanor, and rapid breeding cycle have made them ubiquitous and dangerous pests on many worlds. Virtually everywhere the krogan have been, varren infestations have followed, wreaking havoc with the native ecology.
The krogan have had a love-hate relationship with varren for millennia, alternately fighting them for territory and embracing them as treasured companions. To this day, krogan raise them as beasts of war. A common subgenus of varren has metallic silver scales, leading to the rather unusual nickname 'fishdogs'.