Swarm · 1 hex · SM +0 Swarm of Rats (Monsters on Automatic; answers SRD 5.1)
The classic cellar encounter, and still a real one. A rat swarm goes over a person rather than around them and does not break when hurt. What costs a party is not the bites. It is what is in them a week later.
Attributes
ST9
DX12
IQ3
HT11
HP9
Will8
Per10
FP11
Basic Speed5.75
Basic Move5
Dodge8
DR0
Melee attacks
| Usage | Level | Damage | Reach |
|---|---|---|---|
| Swarming BitesSwarming Bites: 1d-2 cutting, Reach C. No attack roll and no defense. Every bite is filthy: roll HT afterwards or take a fever that arrives days later, when the party is somewhere less convenient. | no roll | 1d-2 cutting | C |
Traits (11)
- Bestial
- Cannot Speak
- Discriminatory Smell
- Extra Legs (Four Legs)
- Fur
- Horizontal
- Injury Tolerance (Diffuse)
- Night Vision 4
- No Fine Manipulators
- Restricted Diet (Carnivore)
- Sharp Teeth
Notes
- Racial cost: -1 points of traits plus 0 points of skills.
- Body weight: 65 lb.
- Movement: ground Move 5 (primary).
- One hex of swarm.
Encounter rating
CER18
Offense20
Protection-2
Threat tierminor
Appearing1
Wandering6
Tags
- monsters-on-automatic
- ai-generated
- doa-authored
- srd-5-1
- swarm
- animal
- mammal
- underground
- urban
- diseased
GCS v5 downloads
Where this one came from
- Source record
- Swarm of Rats [Monsters on Automatic, SRD coverage: swarms]
- Source system
- doa_fixture / doa_authored
- Released under
- cc_by_4_0
- Conversion
- 0.1.0-srd-independent-build
- Review status
- approved
- Credit
- Monster statistics, ratings and description prose by Monsters on Automatic; AI-generated first draft, project-reviewed, released under CC BY 4.0.
- Description
- Written by Dungeons on Automatic, released under cc_by_4_0
- Independently authored GURPS build. The SRD supplies the creature identity this record answers to and nothing else: no SRD statistics, wording or presentation is reproduced, and no third-party GURPS conversion was used as an input.
- Answers the SRD heading(s): Swarm of Rats (SRD 5.1).
- Racial template: -1 points across 17 traits, plus 0 racial skill(s) worth 0 points.
- Every trait is drawn from the project's controlled GURPS vocabulary in scripts/srd/trait-library.mjs, which carries the page reference and published cost for each entry.
- sourceSystem is recorded as doa_fixture because that is the package contract's value for project-authored material; the SRD headings this record answers are in provenance.coversSourceIdentities.
- Ratings are recomputed through the consumer CER path on every build, so a mechanics change cannot leave a stale rating behind.
- Typical Stats, damage and ratings are derived from the racial template rather than authored beside it, so the sheet and the stat block cannot disagree.
- GCS ancestry draft: gcs/swarm-of-rats.gct
- The published Move is the primary medium's cruising Move; sprint figures are stated in the movement note and not folded into it.
- Treasure and grappling are not authored for this record and ship as explicit nulls, which reads as known absent rather than forgotten; `lair` carries a short habitat note instead, because where a creature dens is an encounter fact rather than a loot one.
- Body mass is the figure the build was scaled from and the one fact that makes it checkable; see the gurps-animal-sanity-check skill for the bands.
- Disease is priced as a disabling ability so the rating can see it. The bites alone would rate near nothing, which is not how a rat swarm plays out.
Copyright 2026 Monsters on Automatic. GURPS-compatible monster statistics, ratings and prose authored for this package as an AI-generated first draft under project review. No SRD text, and no third-party GURPS conversion, is reproduced. Portrait and tokens are AI-generated original art. Sources and credits.