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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.