The Ventilation Vermin originated from a failed experiment in the mall's abandoned electronics store, where radioactive materials leaked into the ventilation shafts during the basement flooding. A colony of pests mutated into grotesque abominations, adapting to thrive in the dark, confined spaces and spreading the infection through airborne particles. Over time, they evolved to hunt survivors by using the ductwork as a network of hidden tunnels.

The Ventilation Vermin possesses a malleable, segmented body that allows it to squeeze through narrow vents and ducts with ease. It emits low-level radiation that corrodes metal and spreads contamination, while its sharp, chitinous claws can tear through barriers. The entity moves silently but can produce ultrasonic screeches to disorient prey, and it has a heightened sense of vibration to detect movement within the ventilation systems.

It influences events by controlling key airflow pathways, spreading infectious spores that accelerate the zombie outbreak and creating ambush points throughout the mall, forcing survivors to adapt their strategies and avoid ventilation areas.