Rustling Husks are created from the collected ghosts of frustrated insects who died trapped between window panes. The process through which the souls are harvested and transmuted into this form are currently unknown, but apparently there is a small company in Hungary which manufactures them. Dr. Sugarman also either known how to create them or knows someone more local who can.
Because the insects spent their final days attacking the same sheet of glass over and over in vain, they are known to be fairly ruthless. When one was killed by a cleaning lady, the other 2 preceded to kill her in a violent manner and spread her face along six feet of the hall floor, still recognizable for the entire distance. Despite this, they are completely bound to the will of their creators, the one David later allies with displays no recognizable emotion whatsoever, causing David to feel absolutely nothing towards it despite its kind causing his transformation and indirectly the death of one of his closest friends.
The Catholic Church is also apparently not above employing the use of Rustling Husks, as one was seen as a guard in The Prison of Industry.
While they appear to possess inhuman strength and a long powerful skeletal tail, Rustling Husks generally seem to rely on the use of Screaming Cannons, bony looking handguns that emit a wail akin to the screams of babies or rabbits and instead of simply damaging flesh, actually teleport whatever matter they shoot to an unknown location.
Despite their strength, Rustling Husks are not very durable, generally a well placed strike to the head is enough to destroy one. They also don't last long once made, being empty shells with no life inside them, and they deteriorate quite quickly.
It is unknown whether the Screaming Cannons are directly related to the Rustling Husks, or just a preferred weapon for them. The 2 share a similar motif, but destroying a Rustling Husk will not destroy it's Screaming Cannon, and other characters have been shown using them.
Rustling Husks were a large part of Dr. Sugarman's immortality attempt, killing everyone that was present in Organitek, including David Kim, and stealing the nanomachines. One of them is killed by a Janitor, and the other 2 were taken out by Rabbi Sinnowitz's golems. Later on, Julian Parker uses a leftover finger to track their master, Dr. Sugarman. When they confront him, Dr. Sugarman is armed with 6 more, but they are taken out with ease by Catholic Girl when Sugarman's plan fails to come to fruition.
Later on, when David is entering The Prison of Industry, he is shocked to see one standing there. Nun of the Above reassures him by telling him it's deactivated. However, when Annie Palmer escapes with James Church, David reactivates the Rustling Husk to go after them, initially feeling revulsion for the thing which represented the element responsible for destroying his chances at a normal life. But as he spends even a few minutes with it, he is unable to feel anything towards the unliving thing. It is destroyed with one swipe from the newly released Maranatha and David takes the fallen being's Screaming Cannon into battle.