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Dungeons & Dustbunnies

First Edition
Thumb-sized survivors carve out kingdoms in the ruins of a giant human world, where a sewing needle is a greatsword and a cockroach is a monster
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post-apocalypticfantasy
Rules-LightComedyGonzoBeginner-FriendlyOne-Shot FriendlyTheater of the MindImprovisationSurvival
Languages: English, Spanish
Diced4–d20
System FamilyStandalone
CostFree
LicenseProprietary
PublisherCastamar RPG Studio
Year2026
Complexity Very Low
Accessibility Very High
Runnability High

Core Mechanic

Decrease Dice — each character has one die, starting at d20, that serves as both their health and their resolution roll. To attempt a risky action, roll the die against the Difficulty your class assigns that skill; meeting or beating it succeeds, while a normal failure costs only the attempt. The die steps down a size (d20 → d12 → d10 → d8 → d6 → d4) whenever you roll a 1, take major damage, or voluntarily force the scale to convert a failure into an automatic success. A character whose die would drop below d4 falls Exhausted or dies; sleeping in a safe shelter resets it to d20 and consuming a sugar ration steps it back up one size.

Best For

Groups who want a quick, comedic one-shot or short campaign as thumb-sized survivors scavenging a household that has become a hostile wilderness, with a ruleset light enough to read in a few minutes before the first session.

Highlights

The Decrease Dice mechanic collapses health and resolution into a single die, so every roll both tests the action and visibly wears the character down as the die shrinks toward d4. Forcing the scale lets a player turn any failure into a guaranteed success by stepping their die down a size, making each clutch moment a deliberate trade of long-term stamina for an immediate result. Monsters are rated by a Threat Die that attacks and spells whittle down, and several — the chitin-armored cockroach, the static-charged dustbunny — shrug off ordinary weapons until players expose a weak spot or switch to fire, water, or magic.

Considerations

Combat has no initiative or turn order — the GM narrates enemy intent and players react with defensive rolls — so there is little structure for tactical positioning. Rolling a 1 on any skill check — including routine Stealth, Alertness, or social rolls — steps the die down the same as taking a hit in combat, so avoiding unnecessary rolls becomes a survival strategy rather than a purely narrative choice. There is no advancement system: skills are fixed at character creation and the Decrease Die only ever recovers to its starting size, so characters do not grow mechanically over a campaign.