Hello again, and welcome to the beginning of my series about Tabletop RPG design! As mentioned previously, today's post is going to be all about the core dice systems of RPGs. I'll start with a bit of an explanation of why I think dice systems are important for RPGs, and then analyze a few dice systems from different RPGs. I'll mostly be focusing on systems that I have a fair amount of experience with, as I feel I can give a more detailed analysis of those systems (although I will briefly mention a couple of games that I haven't yet played but seem interesting).
Dice systems are a fundamental part of most RPG systems, and while the details of how dice systems operate can vary significantly between different RPGs, the core concept typically remains consistent: when a character wants to do something, they roll dice to determine whether they succeed or fail. It's important to have this kind of independent resolution system in RPGs for a few reasons. One of the big ones is to create suspense.
With typical storytelling, we experience a story that's out of our own control. Whether it be a book, movie, comic, play; the story is created and presented, either by an individual or a group of people, and the audience gets to experience that story. The audience doesn't know exactly what's going to happen in the story until it happens, and they cannot change the events that unfold. These are good things, they make situations tense, surprise us, and give emotional weight to the stories.
RPG campaigns are also a form of storytelling, but with a different dynamic. In RPGs, the storytellers and the audience are the same people. The GM and players are all creating and experiencing a story simultaneously. This creates a problem; how can an audience be surprised by a story they control? One way to fix this is to have some sort of arbiter. A neutral party that makes decisions about how events play out. Of course, we don't want to have a person dedicated to this role, as it would either be incredible boring for that person by them keeping their decisions completely impartial, or their rulings would become partial to the way they want the story to play out, at which point you may as well just have said person write the story beforehand and act it out as a group.
The way RPGs typically get around this issue is by making randomness the decision-maker. People can't predict random events, so by making plot decisions based on a random outcome, we can get the GM and players to feel the suspense that we want them to feel as an audience. Dice are one of the most simple and accessible ways of getting effectively random results, so they work great for this purpose. From there, we can start to refine things a bit to improve the “storytelling” of the dice. We want characters to feel distinct from each other, and we also want characters to have at least a bit of consistency in how well they perform certain actions. So, instead of just rolling a die to determine an outcome, we can roll a die and add a number to the die roll based on how skilled the character is at the action they want to perform. We could instead have characters roll multiple dice, with the number of dice being based on their abilities. This is how we get to the concept of dice systems. They're a way to keep the story of an RPG interesting to the joint storytellers and audience, in a way that's both fair and satisfying.
That was a bit of a longwinded explanation, but now that I've gone into what I think the purpose of a dice system is in an RPG, we can start looking at specific implementations of them, and the strengths and weaknesses of each system. Maybe a bit unsurprising given its overwhelming popularity compared to every other RPG, I'm going to start with D&D 5e's system.
The dice system for 5e is pretty straightforward, with the majority of rolls being resolved by rolling a d20 and adding a flat modifier to the result on the die. Ability tests, attack rolls, initiative rolls, and saving throws all follow this format. These rolls have a flat modifier added to them based on the relevant stats of the character making the roll. You are typically trying to achieve a higher total result of your roll and modifier than the DC, a number based on the type of test being made. Meeting or exceeding the DC of a roll means success, while rolling under the DC means failure. The other major aspect of the d20 roll is the advantage/disadvantage system. When a character has advantage or disadvantage on a roll, they roll two d20s instead of one. They take the higher number of the two rolled dice as their die result and the lower result if they have disadvantage. Damage rolls and certain class feature rolls, like bardic inspiration and superiority dice, are the notable types of rolls that do not use a d20. Instead, they use variable die sizes, from d4s to d12s, and can have multiple dice rolled and summed to get the final result.
That covers the basics of the system. There's a lot more minor intricacies that apply to specific situations, but that's not what we're here for, we want to analyze the core system's strengths and weaknesses. That said, let's start with what I think is the greatest strength of the dice system: its simplicity.
Tabletop RPGs, while having become a lot more mainstream as of late, are still a niche hobby, and when it comes to niche hobbies you want the barrier of entry to be low. RPGs do have their similarities to more common hobbies like board games or video games, but it can still feel almost completely foreign to someone when they play their first RPG. 5e's system tries to take some of the mental load away from the mechanical side of the game by making the core resolution of a test simple. Want to jump a chasm, haggle for better prices, stab a dragon? No matter what you want to do, you know to grab a d20(or sometimes two) and roll it.
This simplicity is super important for new players, but that doesn't mean it isn't valuable for more experienced players or GMs. While people will become faster at making rolls as they play more regardless of the system, 5e's system is always going to be one of the quickest. Other systems with complex dice systems can come to an absolute crawl if even one of the players isn't used to the system and takes more time to make their rolls. With 5e this is rarely an issue, and keeping the scene moving helps everyone maintain interest.
The GM also benefits a great deal from the d20 plus modifier format. Setting DCs for checks on the fly is a lot easier when the core resolution is simple. The average of a d20 is 10.5, so the GM can know that any task that a completely untrained person can do around half the time would be a DC 10 or 11. A similarly difficult task for a competent individual would be around DC 17 or 18, and so on. This once again helps to keep the game moving, rather than grinding to a halt to figure out the proper level of difficulty with a more complicated dice system.
The last big advantage of 5e's system that I want to touch on is advantage and disadvantage. Much like previous points, advantage and disadvantage are a way to keep dice resolution fast and simple. It is normal in other dice systems to have modifiers to checks, both positive and negative, depending on the circumstances or various abilities of the characters. 5e still does has a few of these, bardic inspiration and guidance to name a couple, but mostly replaces that concept with advantage and disadvantage. The advantage of this format is that it keeps the number of possible modifiers on each roll to a minimum. This, once again, keeps things moving along by having a simple way to manage modifiers to a roll.
I'm starting to feel a bit like a broken record by bringing up all the ways that 5e keeps things simple, and I think I've covered the main upsides of the system, so let's move on to some of the weaker aspects of the system. I think it's best to start with how the system's strength of simplicity can also be a weakness.
If we look at a probability distribution of dice roll results for a d20, we find, unsurprisingly, a flat line. Each result on the d20 has a 5% chance of being rolled. No matter what modifier we tack on to it, it remains that same flat line. That distribution, for me, creates a lot of unsatisfying scenarios. Take, for example, a level 5 character. Such a character is typically viewed as an elite, an experienced professional in their field. Such a character can typically expect to have a 20 in the relevant ability score, for a +5 to their roll, and a proficiency bonus of +3, totaling to +8. Now let's take a character that has a completely average 10 in the relevant ability score, for a +0, and does not have proficiency in the relevant task, giving a grand total of +0 to the roll. This character has little to no experience in the task and aren't particularly suited to it either. There's obviously a difference in skill between these two looking at their bonuses, which is what we would expect.
The problem is that I don't feel that the numerical difference properly reflects the narrative skill difference between the characters. Let's use a DC 19 task as an example. This is something that pushes a professional outside of their comfort zone, a task they can only successfully perform half of the time. Some real-world examples might include a magician successfully performing a hard sleight of hand card trick, or a league bowler scoring above 180 in a game. We would expect the novice to all but assured fail at said task. However, the novice in this case still has a 10% chance of succeeding at the task.
This isn't a great representation, but it isn't too bad either. Sure, the novice seems to have a better chance of succeeding those tasks than they probably should, but once the DC of a check goes past 20 the novice no longer has any chance of succeeding, which mostly makes sense. The bigger problem here, for me at least, is the amount of variance in both characters rolls. If we compare the results of the professional and the novice, the novice has a 19.5% chance to perform equally or better than the professional on any given instance of performing the relevant task.
This all ultimately boils down to a singular issue I have with the system, which is that the flat bonuses a character can get to a check do not scale up enough relative to the range of results from the rolled die. Higher leveled characters in 5e, at least regarding overall combat ability, do still become much more powerful. Though the power that they gain is primarily from the massive hp scaling that most characters have, as well as more potent spells for casters and more frequent and damaging attacks for martials.
So, I think there are a couple big takeaways from this. The first being that 5e's system works really well as a dice system for a gateway to RPGs. The things it does well are great to help people who haven't played an RPG before but want to play a campaign in a fully fleshed out game. The simplicity of the system also isn't only a benefit for new players; I think most people can appreciate the way that the system's simplicity keeps the game flowing. The system does have its fair share of issues, mainly stemming from the same simplicity and speed that work in its favor. Though, the problems I've listed don't really matter if you just want a system that resolves situations quickly so players can spend less time rolling and more time roleplaying.
I'm starting to get the impression that I underestimated how long this topic would end up being. This post is already quite long, so I think I'm going to leave off here and pick things up in the next post with a couple more systems.
Until next time.
-JGDev