Pathfinder RPG Spelldesign rules wrote:


The Golden Rule

Compare your spell to similar spells, and to other spells of its intended level.

Unlike when pricing magic items, there are no formulae for how to correctly "price" a spell. The entire process is a matter of comparing the new spell you're creating to other spells and evaluating whether your spell is weaker, stronger, or about the same as that spell or group of spells. Designing a spell requires a firm understanding of all the game's rules, not just those related to spells. Furthermore, it requires an understanding of some unwritten game assumptions, most of which are discussed throughout this section.

Example: If you look at the Spell Lists, you'll notice that there isn't a 1st-level wizard spell that deals sonic damage. You may decide to design a spell to fill that niche, modeling it after burning hands, except dealing sonic damage instead of fire—perhaps you'd call it sonic screech. However, there's a reason there aren't as many sonic spells in the game: "sonic" as an energy type is a late addition to the rules, and very few monsters have any resistance to sonic damage because most monsters existed before "sonic" was defined as an energy type. Because there are fewer creatures with sonic resistance than creatures with fire resistance, sonic screech will almost always be a better spell than burning hands. That means if you introduce sonic screech into your game, you'll see savvy players selecting it instead of burning hands. If a new spell displaces an existing spell from the roster of most spellcasters, it probably means it's better than the other available choices—and if it's so good that it's obviously the best spell choice, it's probably overpowered. Understanding the entire system of rules can help you avoid mistakes like this.

Kid_Kyoto in 2006 wrote:
Rule #1, always forever is: keep it simple. Whenever possible use universal rules and stats from existing armies. Less to remember and people will accept it more.

Rule #2, don't rewrite the game in your new codex. if you want to rewrite this game do it. If you want to add a new army, do that, don't do both. When you want to do something ask yourself if it can be simulated using current rules. If you really, really, really want to bring back overwatch, or save modifiers or whatever, then do that, don't do it as a special rule for your DIY army. I know, I know GW rewrites the rules all the time and many of the rules (turbo boosting, rending stuff, fleet of whatever) have become official. Well guys when GW's stock falls again and you can buy the company with pocket lint then you can do that too, for now, write an army within the rules.

Rule #3 is, if you want to limit something limit it, make a 0-1 pick or eliminate it entirely. Overcosting a none-too-effective pick just means no one will take it.

Rule #4 is, keep it abstract, 40k is not a very detailed game. No ammo rules, terrain is lumped into some general categories, all 20th century rifles are 'autoguns' etc. So don't go overboard with overly specific variations. This is just a derivative of keep it simple but it's worth saying outright.

Rule #5 do not throw in the kitchen sink. No army is all things to all people so don't try and create the omni codex. Limit yourself to 2-3 choices per category. Less for opponants to remember, less to go wrong. Think of the eldar and how terrible their rules have always been becasue GW decided they had to have everything from killer clowns to citizen militia to gods. You can always go back and write another book later.

Rule #6 when in doubt, underpower a unit. It's your codex but other people have to approve of it. Try not to piss them off with super mega guys who are T8 and have a 3+ save and swing their powerfists at initiative and move and fire heavy weapons AND fire two flamers AND cost 80 points. I mean come on, something like that will never fly.

Rule #7 don't break more than one rule at a time.