The Thorax Swarm is a Tyranid Biomorph characterised by large bloated chest cavities filled with swarms of small parasites. These creatures erupt from openings in their host's chest to drown the enemy in a deadly cloud that chews out eyes and crawls down throats. Different types of small creatures may make up these swarms:
- Electroshock Grubs - Generate powerful bolts of electricity arcing between themselves as their constantly writhing segmented plates produce electrostatic energy. Anything caught in between this energy is reduced to a charred ruin.
- Desiccator Larvae - Latch on and, within seconds, suck every drop of moisture from their victims, leaving only a dry husk.
- Shreddershard Beetles - Instinctively crawl into any nook and crevice on their victims such as those between armour joints. They are covered in needle-sharp spines and cannot live for long outside their host, but as they die they explode, covering their victims in a shower of needles.