We are working on a setting with low magic for Pathfinder, and we initially started out on creating lots of custom rules to go with that. However we found that the more rules we created, the more we had to change other rules. How far do you go with customizing a rules system before you end up with a completely new one?

  • \$\begingroup\$ I'm curious - what kind of customizations? \$\endgroup\$ – LeguRi Aug 19 '10 at 20:40
  • \$\begingroup\$ Please answer here: rpg.stackexchange.com/questions/150/… :D \$\endgroup\$ – LeguRi Aug 19 '10 at 20:42
  • \$\begingroup\$ Customizations that alter how core classes work (or if they exist at all). Customizations that change how core mechanics work like spell casting. These are some examples: byswarm.com/search/node/magical%20pathway \$\endgroup\$ – Mike Bohlmann Aug 19 '10 at 20:49
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    \$\begingroup\$ Why does it matter? "How long can you add yellow to blue before you have green?". I can see it mattering from a copyright point of view for instance, but otherwise, why would you care as long as you're happy with the result? \$\endgroup\$ – Tobiasopdenbrouw Aug 21 '10 at 19:19

Houserules are an essential part of the hobby, and you have my blessing.

To answer your question, you'd have to get pretty far. For a good example of how far, check out Labyrinth Lord and Mutant Future. Mutant Future is based off the Labyrinth Lord system, but changes the setting, the class system, spellcasting, and the technology levels to the point where it's absolutely unrecognizeable.

If you look back one day and realize that you've got more new parts than old parts, basically, you've created a new system.


Once the core mechanic of the game is changed, it becomes a new game. An example of a core mechanic would be using the d20 + modifiers in D&D to resolve combat; or rolling pools of d10 in World of Darkness.

Alternatively, if the game has a specific setting, but the setting is tossed out the window and replaced with one of your own, it's a new game, specifically yours.


Personnally, I only tend to modify rules when I REALLY need it, or when some rule seems completely dumb to me. So I would advise you to stop here creating too much custom rules, and pretty much create them on the fly when you need them.

  • \$\begingroup\$ -1. This does not answer the question. \$\endgroup\$ – GMJoe Jun 6 '12 at 5:09
  • \$\begingroup\$ Could you provide more explanation, before randomly downvoting ? \$\endgroup\$ – Valentin Rocher Jun 7 '12 at 7:40
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    \$\begingroup\$ The question was about what quantity of new rules makes a game transition from being one game to being another. Your answer was that changing the rules is something to be avoided. In effect, you have answered the question "Do you think creating custom rules a good idea," which is not what was asked. Also, my downvoting was entirely deterministic. \$\endgroup\$ – GMJoe Jun 8 '12 at 5:26
  • \$\begingroup\$ To put it another way, your answer was to "should I?" wheras the question was "what happens if I do?" \$\endgroup\$ – GMJoe Jun 8 '12 at 5:45

Once you start bending or changing rules its a slippery slope. The guys that made the game put a lot of thought into this, they know what they are doing.

The only time there needs to be rule modifications is if you encounter a situation that is not covered in the rules.

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    \$\begingroup\$ It's more about making thematic elements reflected in the game system as opposed to changing the system for balance or preference reasons. \$\endgroup\$ – Mike Bohlmann Aug 19 '10 at 20:49
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    \$\begingroup\$ Just because they put a lot of time into it doesn't mean that they know what's right for you and for your group. \$\endgroup\$ – LawfulIndifferent Aug 20 '10 at 3:29
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    \$\begingroup\$ The first rule should always be: There are no rules; if something doesn't work for the game you're running, change it - just make sure the players are aware and happy with it. \$\endgroup\$ – Rob May 31 '12 at 12:22
  • \$\begingroup\$ -1. This does not answer the question. \$\endgroup\$ – GMJoe Jun 6 '12 at 5:10

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