From The Backrooms Wiki
Entity 19
Entity Class:            Class 4C
》Moderately dangerous, hostile
》Animal-like intelligence

A spider with an advanced infection of the crawler fungus

“Crawlers” is a collective name for creatures in The Backrooms infected by a type of fungus named the crawler fungus. This fungus infects exclusively arthropods, and can spread via aerosol. While it is unable to infect wanderers, it is dangerous to them in other ways.


The crawler fungus is a fungus, likely in the genus torrubiella, that causes a disease of a variety of arthropods in The Backrooms. There are reports of the crawler fungus infecting velvet worms and tardigrades, although these are not confirmed. There are scare reports of it infecting wanderers, although the effects are limited to minor rashes. The fungus spreads via sporulation.


A single cell of the crawler fungus appears very similar to other fungal cells, having a cell wall, being capable of sporulation, incapable of photosynthesis, and having a mitochondria and cell nucleus. If the fungus finds a suitable host, it will begin to produce hyphae, creating white mycelium all over its host. As such, any creatures in The Backrooms that are pure white are to be avoided at all costs.


While other torrubiella species are parasitoids, the crawler fungus manages to live inside its hosts without killing them. They manage to replace their hosts with a body made of fungal cells.

Infection is rapid and takes place in only a few minutes.

Stage 1

A creature in stage 1 of crawler fungus infection will start moving around erratically, as if it is itchy. This stage lasts around 1 minute.

Stage 2

Creatures in stage 2 of crawler fungus infection will begin leaking fluid from their skin. Hyphae then proceed to pop up in places where the fluid is leaking. This stage lasts around 3 minutes.

Stage 3

Stage 3 will lead to the sudden covering of the infected creature with mycelium. The fungus will also start producing a large amount of heat through unknown means. This stage lasts around 30 seconds.

Stage 4

By stage 4, the hyphae of the fungus will have spread into the nervous system of the infected creature, hijacking it so that the host will be hostile to all other life. The host will also heat up to around 150 Celsius. This is more than enough for the cells of the host to die, but the crawler fungus is able to resist these temperatures. The exoskeleton of the host will be taken off by hyphae, and the fungus will use it as a weapon, similar to a knife. This stage lasts 5–10 minutes, with an average duration of 8 minutes.

=Stage 5

Stage 5 results in the complete destruction of the host creature, as the fungus takes over and repurposes all bodily functions to suit itself. The fungus will live in this form forever. Due to the crawler fungus being able to regenerate extremely quickly and resist many difficult conditions, this phase is hard to kill. It is advised by many groups to simply run away from stage 5 crawlers.

Social behaviours

Crawlers are extremely hostile towards all forms of life, except for other crawlers.



Due to the hardy nature of the crawler fungus, crawlers can live almost anywhere in The Backrooms. However, they are attracted to damp, dark, oxygen-rich places, such as Level 1. The air in a level inhabited by crawlers must also contain some bacteria, as they need bacteria to feed. Crawlers also dissolve in water. Due to the hunting habits of crawlers, they are most commonly found in levels where there aren't many other entities.


The crawler fungus is able to survive by using cilia to grab bacteria and other microorganisms out of the air. Cells not directly exposed to the air are delivered these nutrients by other cells. Despite crawlers being able to survive by eating bacteria, they are extremely hostile towards wanderers and all other lifeforms. Crawlers will attempt to kill wanderers by cutting them apart with what remains of their exoskeleton, and will eat by ripping cells apart with cilia. They are usually unable to eat wanderers in one go, and may take weeks or even months. However, since crawlers are able to eat bacteria that would otherwise ferment the body, their food is usually not taken. If another creature approaches a crawler while it is feeding, the crawler will usually kill that creature too, although it will sometimes run away. Likely due to their thick skin, crawlers fear skin-stealers.

Crawlers are actually edible, and taste like mushrooms. However, they are very rarely eaten.


Inside a colony, cells of the crawler fungus reproduce via binary fission to replace dead cells. However, crawlers do produce spores to infect other arthropods at certain times. Crawlers will collectively produce over 1,000 spores, but only around 6 will go on to infect a new host. Crawlers do not age and are able to heal from major wounds. The only known way to kill crawlers is through toxic substances, water, or cutting them in half. The lifespan of the average crawler is unknown, as they do not show any markers of ageing.


Crawlers were discovered in 1239 after a spider raided The Lost's base on Level 1. The creature was shot several times and managed to survive, only being killed after it was cut in half by a wanderer. The crawler managed to kill around 7 people. Ever since this incident, crawlers have been very common in many Backrooms levels, being able to spread between levels by clinging onto wanderers when they noclip.

Dos and Don'ts


  • Kill crawlers by cutting them in half.
  • Stay away from animals covered in white mycelium.


  • Kill crawlers with gunfire, unless it is from a squirt gun.
  • Approach entities to see if they're crawlers.