On A Core Resolution Mechanic

Over the last two posts, I’ve talked my way around both why I started this blog and some really simple ideas for enhancing low-level play. One thing you’ll note that I haven’t talked about is a core resolution mechanic for this unnamed fantasy heartbreaker system I’m building. Why haven’t I talked about it yet? That’s simple, dear reader: I have no idea what it is yet.

I know, I’m shocked too.

What I do have are several ideas for a core resolution mechanic that I’m going to lay out here with what I consider the pros and cons for each one. Maybe by the time I’ve written all this out, it will have helped me make a decision. Or at least helped me say “wait, this mechanic is garbage” to at least one of them. We’ll see!

But Wait, What’s a CRM Anyway?

I’m glad you asked, person-who-is-reading-a-tabletop-RPG-blog! A core resolution mechanic (which I’m going to start calling CRM from now on, because typing that out is getting on my nerves) is essentially the engine behind gameplay. To use the most ubiquitous example, the CRM in Dungeons & Dragons is ‘roll a d20, add or subtract modifiers, and compare it to a target number.”

In other words, a CRM is how actions within the game are resolved in most scenarios – some games have different mechanics depending on what you’re interacting with or what system is being used, but the CRM is the most-often used mechanic to determine success or failure. There might be a different system for resolving something specific (for example: in 5th Edition, healing during short rests is used by rolling the class Hit Dice to regain hit points), but generally you’re going to be using the CRM during gameplay.

The d20 system is everywhere, thanks both to the popularity of Dungeons and Dragons and to the proliferation of games based off it with the release of the Open Game License back in 2000 – the OGL allowed anyone to use certain mechanics and aspects of Dungeons & Dragons to build their own game (as long as they didn’t use any Product Identity from D&D – meaning the actual name D&D, copyrighted monsters/settings/items/spells/etc). It’s likely the most popular system out there, but it’s not the only system by a long shot. Rather than go over EVERY SYSTEM ever, I’m going to talk about the three systems I’m considering – or at least considering variations of them.

The d20 System

Of course I’m considering the d20 system – specifically the OGL as it applies to the 5th Edition System Resource Document. As I’ve said before, I’m a big fan of 5th Edition and I think it would be a pretty good jumping-off point for a game but I do have some reservations about it. Pros and Cons time (but only for this system – the other ones won’t get full Pros and Cons because I’m not as familiar with them)!


  • The mechanic is already built, playtested, and roughly balanced (….kind of).
  • It’s already familiar to a large percentage of tabletop gamers, so it would be easier for people to try a new game with a familiar system.
  • It’s pretty easy to houserule/homebrew, making it easy to add and remove mechanics to and from.
  • Using the SRD, I would already have a leg-up on building a LOT of the additional mechanics I’d need (combat resolution, magic, classes, monsters…)


  • Because it’s so prevalent, it seems like it’d make it harder for a new game using it to really stand out.
  • Personally, I think it’s a bit boring. But I have been playing d20-based systems since something like 1996.
  • Because all this stuff is pre-built for me, it might keep me from exploring alternate systems that may be more interesting or easier to tack on to a different CRM.

At the end of the day, the d20 system presented by 5th Edition is a solid system that’s easily modifiable but kinda boring. I’m not opposed to using it, but I feel like there’s something more interesting out there.

Dice Pools

Dice pools are essentially… well, it’s a pool of dice. Not a great definition, I now. Basically with a dice pool, you get a set of dice you roll to determine success or failure. The size of the pool can be determined by any number of things – your Attributes, Skills, Equipment, Magic, Traits… it depends on the game in question. There are two kind of variations to dice pools to quickly go over here:

First, there’s what I call the summed pool – essentially you roll your pool of dice once the pool has been determined, add everything together and compare that to a target number. Examples of games using this style of dice pool include Star Wars (the West End Games version, also known as “the only Star Wars tabletop RPG worth playing”), Over the Edge, GURPS, and Legend of the Five Rings.

Personally, I like summed pools but feel like they take just a bit too long to resolve at the table – as your dice pool gets bigger, it takes a little longer to add all the dice together and can somewhat slow down play. It doesn’t slow down play a lot on each roll, but over the course of a single game session it can add up. I do love the versatility of a dice pool system, but I think there’s a slightly better way to do it.

And that leads me to what I call the success pool – instead of adding the pool together and comparing the sum to a target number, instead each die is compared to a target number and called either a success or a failure, and the number of each is compared to determine if an action is successful or not. Examples of games using this style of dice pool include Vampire: the Masquerade, Shadowrun, and Deadlands. In my opinion, it’s a slightly better dice pool variant.

Personally I find it a bit easier to look across the dice and quickly determine which are at or above a target as compared to adding a pool together. I also like the idea of comparing successes to failures to determine the scale or or level of success/failure.

Percentile Dice

Ah, the percentile dice. I personally have not played a game that used this as a CRM but I’ve read several (one of my hobbies is reading tabletop RPGs just to glean new mechanics) and I both think they have promise and also don’t understand why they aren’t converted to a d20. The basic premise is rolling a d100 (usually expressed as two d10s – one for the tens column and one for the ones column – rolling two 0’s is equivalent to rolling 100) and comparing it to a target number. Examples of games that use the percentile dice system are RuneQuest, Millenium’s End, and Call of Cthulu.

I think they have promise because I do think there are some reasons to have more granularity than a d20 system. If you look at percentages a d20 gives you a flat 5% chance of hitting any number – it basically equates to rolling a percentile dice but only every 5th percentage matters. Having a 1% granularity difference can be useful, especially in games with large skill lists or allowing a longer character growth by doling out fewer skill points into a larger resolution mechanic.

So Those Are The Systems – Which Are You Choosing?

Well… that’s a tough decision, but one I really need to make before I can do much building or playtesting. It’s hard to look at setting up combat or exploration or social interaction or exploration or a skill system if I don’t know…. how any of them are going to be resolved. Thankfully, writing this out helped solidify my decision. I was already leaning one particular way, but writing this post out and taking a look at different systems really did help.

I’m going to be using a dice pool mechanic – the only problem is, I still can’t pick between a summed pool or a success pool. I think both are very nice and have upsides and downsides, and I’m going to start building systems in both ways. This may be completely unnecessary, but I think they’re similar enough that I can build part of it the same way across both (how you determine what your dice pool is, the size and number of the dice), and then differentiate them with the resolution until I decide which one I like better.

Next week, I plan on taking a closer look at the dice pool mechanic I’m planning on using by taking a look at Attributes and Skills. See you next week, dear reader.

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