Sep 052014

We, here at Banner House Games, really like the latest edition of Dungeons & Dragons. We’re not, however, in the habit of reviewing popular games that already have dozens upon dozens of reviews. This, being a design blog, we’re much more interested in the various mechanics and design philosophies put forth in D&D 5e. Today, I wanted to share my observations and examination on the new Advantage system and how it affects conditions. Also, I wanted to touch on the idea of rules simulating reality on a sliding scale. Wow…. that might be a tall order. Don’t hate me if I can’t deliver.

Warning! This is not a short article.

(edit: the second portion of this article was based on incorrect math. It is being revised currently and will be posted at a later time. In the mean time the first half is still relevant and has remained. Also, I’m embarrassed.)


The Advantage system is a sort of blanket mechanic meant to cover any and all modifiers to rolls. It reduces the amount of mathematics you have to perform on any given roll. When granted, whether through class abilities or by the DM, the player or other rolling entity rolls two d20s instead of one and takes the higher result for their roll. This rule has an opposite. If you have a disadvantage, you’ll roll two d20s and take the lower result. Now, there is math involved in this mechanic, but it is elusive to those who don’t obsess over dice probabilities. Luckily, I’m going to summarize the numbers for you. They change depending on the target DC, giving an inverse bell curve of modifiers. If your target number to over come is mid range (I.E. 8-12) then the benefit/penalty is large, around +/- 5. However, if your target number is an extreme low or high (I.E. 1-2 or 19-20) this benefit/penalty is small, around +/-1. There is a discussion around this bell curve all by itself that is worth investigating, but that has already been done by others. Since our example needs a stable number to illustrate it’s point, we’ll just make a declaration that for the rest of this article, advantage is equal to a +2 bonus and disadvantage is equal to a -2.

Modifiers in Dungeons & Dragons have traditionally been placed on any number needed. So if your leather armor has acid splashed on it, maybe it’s damaged and grants a penalty to your AC (Armor Class) if you wear it. Or perhaps the enemy has fallen onto the ground and so you are granted a bonus modifier to your attack roll to hit the enemy because of his position. Any time a number is presented (AC and Attack Bonus for example) you could theoretically apply a positive or negative modifier. This creates more calculations on the part of the players. While the math certainly isn’t complicated, it wasn’t uncommon for players and DMs to add and subtract three or four separate modifiers. Sometimes more. This is time consuming and obnoxious, especially when it happens dozens of times in a given play session for multiple people.

However there is an interesting play of math that these modifiers can create. Let’s look at two specific modifiers. A -2AC and a +2Atk. I may not look as much, but these modifiers are mathematically exchangeable across characters. In other words, if you have a -2 to your AC, that is mathematically the same as giving me a +2 to my Attack roll. I’ll attempt to explain.

In the D20 core mechanic, you will roll a twenty sided die and add (or subtract) a modifier to the result of that roll. The die will give a result between 1 and 20 and the modifier will raise (or lower) that result by that amount. There is a median result on the die, 10 that is used as the base number for determining difficulty. In other words, when planning out how high or low a monsters AC (or other values) should be, it is faster to assume that 10 is the typical roll. Knowing this, we’ll look at some attack modifiers vs AC values. Let’s assume that you have 16AC and I have an attack modifier of +4. The game assumes that I’m going to average a totaled result of 14, thereby missing your 16AC. If you had a -2AC, that would give you an effective 14AC. My result of 14 would hit you. Or if I had a +2 Atk, that would raise my Attack modifier from +4 to +6, giving me an effective average of 16, hitting your AC or 16. Now, of course I could get any other number with fair odds, but there’s one last detail to remember.

Static numbers, are just a rolled d20 with a set result of 10. So an AC is determined by taking the number 10, and adding the relevant armor and dexterity modifiers. A Spell save DC is just the number 10 + the relevant modifiers. In fact, you can think of a spell save DC as being an attack roll, and the save itself as setting the AC for the spell to hit. Spells of this nature are assumed to hit automatically, but a person could be unaffected by the spell, so they roll a save. The number for them to beat is the Spell Save DC. In effect, you’re both just creating two numbers and comparing them. One is rolled randomly in the moment, and the other is predetermined based on the median of 10.

So, why does this happen? Why don’t both players just have set attack and defense values? Or why aren’t both numbers rolled each time, every time? Many reasons exist, but I posit that there are three primary reasons.

Firstly, that rolling gives you a sense of agency and control. By rolling the dice, you feel like you are contributing. If you just named a static number, it would feel out of your control, but ironically, since you are rolling dice and putting the result up to fate, you’ve now seemingly done something.

Secondly, simulation. Rules in a role playing game are meant to simulate a world to live in. You don’t actually cast spells and swing swords, but you want to create the effects. In the very first edition of D&D there was no distinction between weapon types other than their name. Players would simply have to imply the difference between an axe and a sword in a combat situation. But players decried that they wanted the rules of the game to simulate the reality of the weapon. Afterwords, axes did different amounts or types of damage than swords. The rules were changed to simulate real life. So for dice rolling, if a spell seems like it would hit a player regardless… then it does! But they would roll a die to mitigate the results. If a character had armor on, he would probably not be able to change his defense up too much, but my swinging of a sword could vary drastically. So some numbers are static and others are rolled to simulate the expected aspects of combat. Players expect the world to work as they’ve observed our own world working.

Thirdly, for time. Combat can take long enough as it is before you have to make sure to get two separate players to wake up and engage. Or in most cases, one of those players is the DM, which means that on top of all the description, world building, and management he’s got to keep up, he also has to roll attacks and defense for every single turn of every single player and his own monsters. Oddly enough, there has been a sense of drag in combat for years, regardless of this attempt to reduce the total rolls needed. In this latest edition of the game they’ve attacked that hurdle again by introducing the advantage system.

The advantage system’s perks are primarily the lack of calculations in combat. Now just roll, see which is higher and add a single modifier to combat. It has an interesting requirement, however. It only works on rolls. If I theoretically gave you an advantage on your defense, then that immediately proves pointless when your defense value (AC) is a static number. So, rather than making both attack and defense dynamic numbers, stepping backward, they instead simply force all modifiers to affect the active roll. Advantages can only ever be applied to rolls and not static numbers. This is important. Sorry for repeating.

Okay let’s take a second and summarize what we’ve discovered here so far.

A -2 AC on player 1 is = to a +2 Atk on player 2

Modifiers no longer exist, being replaced by advantages and disadvantages.

Advantages and disadvantages can only be placed on active rolls.

You may be wondering what prompted all this examination. “Who cares? It seems fine”, you say. I agree with that, I think it’s fine. But you are just a voice in my head. I can’t let you speak for everyone. I need an advocate for those who have a problem! What’s that? You in the back? You’re worried about simulation? You look like a straw man to me… Oh what’s that? You’re based on actual discussions the writer has had with people while working with and playing games in the community? Okay, that should work. Now we get to the heart of the matter.

Let’s use an example condition in the latest edition of D&D. Blinded.

Blinded says:

      • A blinded creature can’t see and automatically fails any ability check that requires sight.
      • Attack rolls against the creature have advantage, and the creature’s attack rolls have disadvantage.

That second point is what we’ll focus on. Now, we’ve already translated advantages and disadvantages into a static numerical modifier, so let’s do that now and redefine Blinded to match.

    • Attack rolls against the creature have +2, and the creature’s attack rolls have -2.

The creature’s attack rolls having -2 makes sense. Without sight, they can’t aim nearly as well, and so suffer a penalty. However attack rolls against the creature have +2 is… a bit odd. How can you hit me better because I’m blind? Wouldn’t it be more accurate to say that my ability to defend should be at a -2 since you can see me? After all, if I’m the one affected by blind, why aren’t all the modifiers on me? This of course is because the advantage system can’t be used for static numbers. So if they would theoretically like to give you a -2AC for being blind, but can’t use AC because it’s static, they’ll have to exchange the -2AC on the defender with a +2 Atk on the attacker. Since they are numerically exchangeable, the condition now has modifiers that only affect the active rolls and can now work within the advantage system. We can now see that the +2 on the attacker is just how the game expresses a penalty to defense. Now it works cleanly, but some players don’t like how it feels.

I’m going to make it more complicated now. What if two players are both blinded and one attacks the other? The rules state that player A has a disadvantage on his attack against player B and that player B is giving player A an advantage on his attack against B. Player A is now receiving both and advantage and disadvantage on attack against player B. A -2 and a +2 add up to a zero.. so the two cancel out and Player A has no advantage or disadvantage to his attack roll against player B.

“FOUL!”, you cry. “If the two players don’t have advantage or disadvantage against each other and they’re both blinded, then that means their fight against each other is the same as though neither of them were blinded.” and, mathematically, you’re correct. The math is just an abstraction, it is the same as if you had affected the correct numbers. What’s happening is that your inability to hit me, is canceled out by my inability to dodge. Because of the system forcing the effects onto active rolls only, it seems to have switched, but the math shows them to be equal.

In the rules as written in the Player’s Handbook. The advantage being granted by the other blinded character and the disadvantage being given by your own blinded condition, cancel out, and no advantage or disadvantage is given when attacking each other.

In my research of of this ruling I asked many other DMs how they would rule it. Overwhelmingly, most said they would just give each player a disadvantage to their attack roll. This is because of simulation. Players and DMs expect the world to work a certain way and want to homerule the game to fit their expectations. For example, one person stated that an inability to hit is intrinsically larger than an inability to dodge. However, I argue, that such a distinction has no place in this game. Unfortunately, in order to back up that argument… I have to retract something I previously established for simplicity’s sake. Earlier I translated an advantage as a +2 and a disadvantage as a -2. This won’t work for the following paragraphs. So.. I’d like to revert it back to a dynamic modifier based on the difficulty of the task, the target number. Sorry about that.

First, let me make a small observation. While this is very true and equally important, it’ll be easy to overlook it or downplay it’s importance, so I just wanted to mention it before I move on to the more complicated observation. The situation described above, only concerns the two affected players when they attack each other. If either of them attacks a non-blind character, they would simply be at a disadvantage.





Let’s look at the advantage system again. If your target number is in the mid-range, then the advantage or disadvantage is a smaller bonus/penalty than if the target number is on the outer range. A difference of +/-1 all the way up to a +/-5. So let’s take two characters named Wizard and Fighter who each have the same job as their name. Both have been thrown into a ring and given a sword. The fighter has his armor and the wizard doesn’t have his spells. So we’ll make up some stats for them

Wizard the Limp-Wristed

HP 8


Attack +2

Likes: Librarians

Dislikes: Investigative Committees


HP 32

AC 18

Attack +6

Likes: Murder

Dislikes: Investigative Committees

Okay we’ve got our two competitors. They face off. If Wizard wants to attack Fighter, he’ll have a rough time hitting him. With a AC of 18 and a +2 modifier on his attack roll, that means Wizard has to roll a 16+ in order to hit Fighter, and he’ll have to do it many more times due to Fighter’s high HP. Needing a 16+ to hit means he has a 25% chance to hit. Conversely, with his +6 to attack, Fighter only needs a 6+ to hit. That means he has a 75% chance to hit, and may even finish the fight in one hit.

Oh no, Wizard has slipped and fallen to one knee! Fighter now has an advantage to hit Wizard.. so let’s see… oh.. hmm well with Wizards low AC, Fighter isn’t really getting that much of a bonus, he’s so skilled and his opponent so weak that with the advantage system, he’s only really getting a +1 to his attack roll. That means he has an 80% chance to hit.. wow.. still such a great position, but the advantage barely mattered. Oh my, by pure chance, Fighter missed. What a lucky Wizard!

What’s this? Now Fighter has tripped in some mud and has lost his footing, this could be a good moment for Wizard, he has advantage. And what a huge advantage it is! That second die gives him a massive bonus because of that high AC, maybe +4 or +5 That means that he’ll now hit on a 12+ that’s a 40% chance to hit! From 25% to 40% is a big deal. Still smaller than Fighter’s chances, but the modifier was important. He hit! But Fighter is still standing… Wizard’s got a long way to go.

Look, something in the sky! It looks like a giant wind elemental has come into the arena whipping up a small sand storm. I can’t imagine either Wizard or Fighter can see in this, they’re both blinded. Let’s assume they’re both at a disadvantage to attack each other. If Fighter gets his chance to strike, his +6 goes down to a +5… not a huge change.. However if Wizard gets a moment, then he’ll have a huge disadvantage, making his +2 a -3 meaning he’ll have to roll a natural 20 to hit! A 5% chance.

It seems that advantages between players are not created equal.

The effect of being blinded affected each player at a different severity. The Fighter, who is well trained in combat and well protected by his high AC is less likely to be hit by a blind opponent who is not well trained when both characters are blinded. Meanwhile, the trained Fighter is less hindered by the disadvantage to hit the weak poorly trained Wizard. Let’s look at those percentages to hit.

Neither player has disadvantage or advantages

  • Wizard 25% to hit
  • Fighter 75% to hit

Bother players have Disadvantages

  • Wizard 5%
  • Fighter 70%

But something is missing… We’re forgetting that being blind also affects your ability to defend. We’re not adjusting the AC of each character to match the effects of being blind on both of them. Remember, the advantage system does this by granting an advantage to your opponent on their attack. Since we’re examining that exact scenario however, we’ll need to change it and look at it from a different view. So let’s change the AC’s by their approximate modifiers.

This is complicated. How do we do this? The same way we modified the attack rolls. We determined the dynamic modifier based on the target number, the AC. Since the attack roll is dynamic, we’ll make it into a static number by changing the rolled d20 into a 10 and adding on the attack modifier. We’ll also want to change the ACs into a roll by subtracting 10 and using the remainder as a modifier. With our numbers converted, we can now change both the AC and Attack mod for each character.

Now let’s plug those in.

With disadvantage

  • Wizard AC 9
  • Wizard Attack – 3
  • Wizard has 5% to hit


  • Fighter AC 17
  • Fighter Attack + 5
  • Fighter has 85% to hit

With the modifier to AC, Fighter got an increase of 15% chance to hit. Wizard can’t go any lower than 5% but we know that if it was possible, he would have less than a 1% chance. To clarify. The penalties I made to their AC and attack were as follows:

Wizard AC -3 Attack -5

Fighter AC -1 Attack –1

So in the case of the untrained wizard, the penalties were larger for his attack than to his ability to defend. For the fighter? Not so much. It looks like the effect of being blind is also not created equal. Our previous argument stated that in this situation, one character’s inability to attack well was canceled out by the others’ inability to defend. This seems to be true if characters are fighting an opponent with high stats, but completely untrue if their opponent is significantly weaker than them. The fighter in this example has the same penalty to his attack as his defense. Showing that there are cases that occur where the disadvantage does not beat out the advantage.

So, what argument am I making? Seems like I’m reinforcing the counter argument that if players were both blind, then they would both have disadvantage to attack. But looking at the difference in effectiveness while bind I have to ask, “Does this simulate reality?” Perhaps, though I’m not sure of that. More importantly, they seem to affect characters differently depending on their abilities. Plus, the sheer math involved is just plain silly and I’m glad that it’s taken care of automatically. I’m also looking at the stats to hit without disadvantage. They seem to already reflect one character’s natural talent and training over another. It just seems to be a matter of how much and whether being blinded should affect each character differently. The number given when both characters have disadvantage are extreme. With one character almost automatically being able to hit the other even while blind. Shouldn’t a disadvantage to both character’s give a flat penalty to both?

So, it seems to come down to simulation. Which fighter would do better given their conditions, the environment, the familiarity of their fighting style, their natural talent, training, etc. A comparative chart showing all possible interactions between two fighters given all these variables and a dozen others seems important to a realistic game. So let’s make that chart.

Just kidding. Who would want that? That’s not a game, that’s a statistics paper! Better yet, I should just go to a dojo and learn how to fight with my actual human body! But the point of these games is so I don’t have to do that and so I can fight wizards and dragons and all manner of creatures with magic and gods and have copper coins plinking down on the bar. Also, with mythical creatures like dragons, who could possibly determine whether the dragon’s ability to fight blind is higher or lower than a human? Those things are completely unknowable.

The resolution of detail in simulation is like the problem of measuring a coastline. At first it seems simple, just measure it out. But what unit of measurement do you use? Do you measure in miles? Or yards? Do you go all the way down to grains of sand? How about molecules in the sand. Not to mention that the coast is constantly changing due to the waves crashing against it. And the TIDE, let’s not forget about the tide. There must be a line drawn somewhere when defining simulation vs game play. Typically this assertion is followed by “Sure, but where is the line drawn?”

Here… it’s drawn RIGHT HERE. The distinction between subtle advantages and disadvantages based on expectations of a reality being simulated with rules that use a number scale of +/- 5%. Any rule system that your table chooses to play with is simply an agreed upon simulation of a fantasy setting. The examination here doesn’t seem to resolve anything in regards to which is a more accurate ruling. It does however make this point. That it took six pages of careful examination to determine the exact mathematics that simulate the realism or non-realism of the effects of being blind within this rule system. In my opinion. The distinction of whether being blind affects your ability to hit with a sword more than it affects your ability to defend, was moot. Now having spent a significant time looking at it, I can safely say that it’s not moot any longer, and that judgment should be passed down. What do you say?

Thank you for your time. I hope that you enjoyed this detailed examination of game mechanics.

Oh.. and go play D&D 5e. It’s really great.