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The Xero Sum Engine (or XSE) is a framework for running Tabletop Roleplaying Games (TTRPGs). The core mechanics are robust and easily adaptable to any genre or setting, while remaining streamlined and lightweight.


XSE supports games for 2-6 people. One player is the Game Moderator who acts as referee and storyteller, and the others are Players who take on the role of characters in the stories.

XSE was initially designed for the post-apocalyptic game Distemper. As this is a grounded, modern-day setting, the rules and equipment reflect that reality. There are no rules included in the v1.0 of the SRD for more fantastic elements, such as Magic or Psionics.

This SRD will be periodically updated as new rules are tested and added.




XSE provides a grounded experience where characters are ordinary humans and not master spies, super-soldiers, or the stars of an action movie.

The XSE combat system can be brutal, unforgiving, and have lasting consequences for characters. Combat should never be entered into lightly but isn't the only potentially lethal threat to characters. Depending on the setting, starvation, sickness, or dying of exposure may be a possibility, and falling from a window might well be fatal.


To survive, players need to focus on social skills such as Gut Instincts, and Negotiating.


The Xero Sum Engine utilizes a simple d6 game mechanic that can intuitively facilitate any challenge or task resolution with ease.

XSE is designed to keep the narrative at the center of the game, prioritizing realism and momentum over needlessly complex rules.



The Xero Sum Engine is fueled by collaborative storytelling and it provides players with various tools to drive the narrative, such as Insight Dice, Filling in the Gaps, Making The Case, First Impressions, Gut instincts, Negotiations, Recruitment, and Community rules.



d6: roll a single six-sided dice.

2d6: roll 2 six-sided dice and add the scores together to get a final tally.

xd6: Sometimes there might be more than 2 dice rolled, such as 3d6 or 4d6. This find outcome is the total score of all dice added together.

d3: roll a six-sided dice and half the result (rounding down), for a result of 1-3.

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