Feature image taken from here.
I have always had a bit of a love-hate relationship with the d20. That icosahedronal sonavabitch has been my ruin many a time. Hell, from the name of this blog you can probably tell that I prefer d6’s.
Part of this is an accessibility thing. Any game that prides itself on “special” dice is actively throwing up barriers to it’s entry. Everyone has d6’s. To get a d20, you need to go to a game store, pick out a set, maybe buy a couple extra d20’s in case one betrays you, roll it a few times to make sure it isn’t cursed, have a maiden true blow gently upon it, etc etc. It’s a bigger hassle than cannibalizing a game of Yahtzee is what I’m saying.
Another part comes down to design considerations. Namely, I prefer a multiple-dice system (3d6 is my personal favorite) because it dramatically lowers the variance in rolled results. What do I mean by variance? Well, this gets a little math-y, but when you roll a d20, you have equal chances of rolling a 1, a 10, or a 20. All of those results have a 1 in 20 probability of showing on any given roll. This means that you’re just as likely to fail utterly as you are to do about average. Which, to me, is some bullshit.
What this does is weakens player agency and decisions. Skills and ability modifiers can only dig you out of a hole so deep, and if you’re routinely rolling 1’s and 2’s, then guess what? a +7 ain’t gonna save your bacon.
Now, let’s compare to 3d6. In 3d6, you roll three dice and add their results together. It’s a little more time-consuming, but has the benefit of a nice, bell-shaped curve to it’s probability. This means that a “middle” result (8, 9, 10, 11) is more likely than an extreme result (1’s, 2’s, 19’s, 20’s, etc). In this scenario, your skills matter more. If you’re routinely rolling 10’s, than all of a sudden that +7 (or even a +2) becomes a lot more significant.
Which isn’t to say a d20 doesn’t have it’s strengths. For one, it’s easy to parse it’s probability. It’s easy to grasp that you have about a 50/50 shot of rolling at least a 10, or a 25% chance of rolling a 15. Multiply a DC by 5, and you have the odds.
It’s also just pretty quick and snappy. You roll one die, add some modifiers, and have your result. You don’t have to screw around with adding up successes or doing a whole shit-ton of math or interpreting some arcane symbology.
But let’s get back to variance. It’s this break in variance that used to put me off DnD. I had session after session of what I’d call “grind-y” combat. You probably know what I’m talking about. It’s when you’re fighting some baddie and you can’t really do much but keep swinging at it and praying that you roll a decent-enough result to hit. You can’t improve your odds, you don’t really have any agency, you’re effectively trapped. TRAPPED, I SAY. At least with 3d6, you can be reasonably confident that a “decent” roll is right around the corner, and you won’t spend 5 rounds rolling 4’s and 5’s. It doesn’t eliminate the problem, but it does mitigate it significantly.
But hey, I mentioned Advantage in the title, right? So there’s light at the end of this math-tunnel. See, Advantage fixes a lot of problems with variance.
Let’s take a look at a graph of probabilities comparing normal, disadvantage, and advantage rolls.
Awwwww yisssss, look at those sexy curves! As you can see, an advantage roll precipitously increases the odds of rolling at least an “average” result (ie 9, 10, 11), without cripplingly boosting higher results (rolling a Natural 20 is still clocking in at about 10% odds. Up from the %5 it usually has, but not such a boost as to make it destructive).
Furthermore, Advantage adds agency. You’re a lot more likely to accomplish something when you have Advantage, which makes it worthwhile to the player to try and get Advantage whenever possible. The Rules-As-Written offers many ways for the players to accomplish this (spells, feats, condition rules, etc) and the Wise GM will offer his players even more by rewarding creativity or cunning plans with Advantage. Players can therefore always have the option of seeking advantage, varying their tactics, invoking fictional positioning, and actions in order to get a better shot at accomplishing their goals.
There’s nothing more frustrating in an RPG than the feeling of helplessness. Of being forced into a bad situation and told to “roll” your way out of it. 5e’s Advantage system does away with the major issues of variance and “grind” gameplay in DnD and other d20-based systems. If players are willing to engage and invest in the fictional positioning of their characters, and the GM is willing to reward them for doing so, there’s no reason to fear the d20.