Partial Success in Roll-Under d20 systems

I really enjoy the way that partial successes in Apocalypse World games continually complicate the fiction. Actions scenes get richer and more interesting as problems mount; the tension builds, and players feel like there’s more thing to react to. However, I’m not a fan of the “moves” system, so I’ve been thinking of ways to port partial successes over to more trad roll-under d20 games, like Whitehack, Symbaroum, or The Black Hack.


A common way to do this is just to say that missing by say 1-3 is a partial failure, while hitting by only 1-3 is a partial success, or something like that. The trouble is that you can end up with some odd quirks, such as a the fact that if you have an ability of 10, it’s more likely to get a full success or failure than it is to get partial ones. The way I see it, characters with average stats should be getting partial results much more often than either of the extremes, similar to Apocalypse World.

Here’s my solution: when making a test in a roll under-system, roll two dice instead of one.

  • If 0 dice pass, the result is a full failure.
  • If 1 die passes, the result is a partial success.
  • If 2 dice pass, the result is a full success.

Here is what the probabilities of this system look like. The sweet spot is from 5-15, as you would expect. What’s interesting is comparing this to the probabilities for Apocalypse World. A 15 looks a lot like a +3, a 13 looks like a +2, and a 11 looks like a +1.

If you wanted more degrees of success than apocalypse world, you just add more dice. Here’s a system with 4 degrees of success: full fail, partial fail, partial success, and full success. With 4 degrees of success, the odds of a full success or failure goes down significantly, so you will be dealing with a lot of partial results. However, the split between bad results and good results will be symmetrical, as opposed to the 3-degrees system, where two out of three results allow the PC some degree of success. I suspect 4 degrees would work better for more realistic games, while 3 degrees would be better for more heroic games.

If you were using Whitehack or The Black Hack, you could still keep advantage and disadvantage by rolling an extra die and dropping the highest or lowest, respectively. Or you could just give players mods to their stat, which might be easier.

I’m planning on using a system like this for the project I’m working on now, The Wormwood Throne(or The Wormwood Crown…I haven’t decided) which will be more robust and detailed than Maze Rats, but the principle is applicable to lots of games.

Maze Rats is now available!

My endlessly-revised RPG is complete, and live on DriveThruRPG! Go there to download it now!

Maze Rats is a RPG and sandbox toolkit for old-school-style adventuring. It contains a single, compact page of rules, a one-page character creation guide, a hand-drawn character sheet, and eight pages of 66-item random tables, rollable with 2d6. Each page contains 9-12 tables, covering everything from spell and monster generation, through NPCs, treasures, cities, wildernesses, and dungeons. If you run (or have always wanted to run) open sandbox adventures, Maze Rats offers everything you need in a compact, easily-referenced format. Also included is two pages of advice for preparing and running open-world games in the OSR style.

The game system itself is 2d6 based. Character are extremely quick to generate, making it great for convention games, one-shots, or introducing new players. The game is highly lethal, and assumes a style of play where caution is essential to long-term survival. It is technically classless, but the leveling options allow players to specialize in fighting, thievery or wizardry or some mixture of the three. Magic is simple and chaotic, with new randomly-generated spells filling the magic-user’s head each night. Everything about the game is designed to be as clean, fast, and intuitive as possible, while driving players towards creative solutions rather than brute force (though brute force is always an option).

Interview with a 5th Grade Dungeon Master

A 5th grade girl at the school where I teach is running a D&D-like game at recess. The rules are posted below. I decided to interview her to get some insights.


Questing Beast: What are all these monsters that you wrote down in the rules?

Dungeon Master: They’re what you can be.

QB: What are the really unusual ones, like the Orazen?

DM: Drazen?

Player: It’s like part dragon, part human. Also, in D&D, it’s also known as the Dragonborn.

QB: What about a Racsaca?

DM: They’re in D&D! They’re like a Tiger-person, with a mane..

QB: What’s a Fawnalese?

DM: It’s like a human that has an animal quality, like ears, or a tail, something like that.

QB: So it’s like a part Faun?

DM: Yeah.

QB: What is a Bungee?

DM: Bunger?

QB: Bunger, sorry!

Player: That’s what I am.

DM: It’s like a normal human, but when they get very mad they can become 3 times the size of a normal human, or three times as small, depending on the dice roll!

QB: They can shrink or get bigger? That’s neat. Ok, what’s a Zazen?

DM: That’s what you are. Remember? It’s like an animal that can speak and turn into other animals?

QB: It’s a shapeshifter?

DM: Yeah, yeah.

QB: Let’s see…what is a Dragonteller?

DM: Oh, you can’t be that!

QB: It says “No killing the Dragonteller.” What’s that?

DM: It’s hard to find the Land of Dragons, but if you find the Land of Dragons, you have to get past the dragons, and once you do all that if you find the Dragonteller, he can answer your questions, he can tell the future and the past…

QB: So he’s the most powerful person in the Dragonlands?

DM: Yes.

QB: Why are there 600 dimensions?

DM: …I don’t know.

QB: Because it’s cool?

DM: Yeah.

QB: Have you gone to any of them?

Player: How many dimensions?

QB: 600 dimensions is what the rules say.

DM: Yeah we’ve been to some of them.

QB: Like which ones have you gone to?

DM: Nether…you can make up any of them…

Player: We went to this sky dimension, that had an evil part of the dimension…

QB: Cloud kingdom…it had an evil part, a good part…the evil part had the Lord of Death.

DM: The Lord of Death?

Player: Lava dimension, the acid dimension, the giant dimension…

QB: So it’s all different elements, basically?

DM: Yeah! No! You can make up any dimension, basically.

Player: There’s the giant dimension, where everything is huge.

QB: What does rainbowneum look like?

DM: It’s like a coin, and it’s rainbow.

QB: It says it costs 100,000 Wadroneum. What’s a wadroneum?


QB: Is is just another coin type?

DM: Yeah.

QB: I’m really curious about he Cloud Kingdom. How do you get there?

DM: In ONE dimension, in one TOWN in that dimension, there’s a tiny door that leads you there.

QB: Wow.

Player: Also, you can be teleported into it.

DM: Someone can be like, boom, you’re there.

Player: You can ride up to it, you can fly up to it…but you have to FIND it.

DM: Yeah, you have to find it. That’s the hard part.

QB: Why did you start making your own roleplaying game, instead of just using Dungeons & Dragons?

DM: …it’s fun.

QB: It is fun, isn’t it? What things about it do you like better than the normal D&D rules?

DM: Well…you can have a special power.

Player: Well, it’s also that creating your own game, your own Dungeons and Dragons game…it’s showing how much you like D&D.

QB: What’s it called?

DM: Adventures in the Land of Dragons.

QB: Makes sense.

Player: It’s pretty much D&D, except there are different mosnters and stuff.

DM: You can be more things than you can in D&D. And you have special skills…and INSTEAD of having having just Intelligence and Wisdom, you can just have Mind, because that just takes less time.

QB: That’s true. That’s why I made mine, because I didn’t like the D&D rules as much, so I just made up my own. Where are you guys right now? What are your characters doing?

Player : So we’re in a dark manor that has a bunch of these doors, and we’re trying to find the owner, kill her, so we can get out of the manor.

Player 2: I want to kill her like a BOSS!


The Real DIY D&Ders

A 5th grade girl is DMing D&D with a circle of boys on the playground of the school where I teach. I sit down to play along. She is having everyone roll a die.

Me: “Where are we?”

DM: “We’re in hell.”

Me: “Why are we all rolling dice?”

Boy: “Hades cursed us to pick up his room. We’re rolling to see if we can put away all the clothes.”

Me: “Can I teleport out of here?” (I’m a magic user.)

DM: “No, there’s too many clothes.”

[Rolling continues until someone rolls a natural 20. Everyone cheers.}

DM: “Hades teleports you all out of there! Roll a die to see where you end up!”

Me: 12.

DM: “You’re in the top of a tree! A palm tree.”

[Everyone else rolls. They’re in a tropical village nearby.]

Me: I want to climb down.

DM: Roll a die! [It works]

Me: I want to find out who’s in charge of this place.

DM: Roll a die! Use your Charisma.

Me: 4 [I’m not charismatic].

DM: You have no idea who’s in charge of the village. A lady walks by and is like, “Who are you?!”

Boy: I want to find out who’s in charge! [Rolls CHA. Succeeds.]

DM: You see a huge mansion on the hill. It has enormous billboards next to it saying “The Guy In Charge.”

Me: I want to knock on the door.

DM: Roll a die!

Me: 12.

DM: No one answers. They’re ignoring you!

Me: I want to kick that door down.

DM: Roll a die!

Me. I’m a weak wizard, but I’ll roll my strength. 17!

DM: You kick a hole right in the door! You stick you head through and see the guy in charge.

Me: What does he look like?

DM: Roll a die!

Me: 14.

DM: He’s a…half orc. A really skinny half orc.

[The whistle is blown and recess ends]

Let’s analyze this. For one, there was almost no railroading (apart from not being able to escape Hades’ bedroom). It was a total improv sandbox, where you could try anything and the DM would come up with a result.

Second: there was no cutesy theme, no polish. Character sheets were hand drawn and photocopied. Character art was about what you would expect, which was half rabid enthusiasm, half bored doodles.

Third: There was no moralizing, no paternalism, no appropriateness filter.

Fourth: There was no emphasis on storytelling of any kind. No narrative mechanics, no personal goals. There was also no combat (although I have observed sessions this DM runs with combat). The focus was on immersion and on doing what you found to be entertaining. Exploration and amusement was king.

Fifth: The DM let herself be surprised. She demanded rolls for everything, even rolling to see what kind of NPC the village leader was. She didn’t have a table or anything, so I have no idea if she just made that up on the spot, or if it corresponded to how dangerous the species was, but it was funny anyway. She treated the dice like a kind of oracle that was guiding the game nearly as much as she was.

In other words, it was utterly unlike every RPG on the market that’s targeted at kids.

There’s no shortage of “Kids RPGs” (No Thank You Evil, Playground Adventures, Do: Pilgrims of the Flying Temple), but they all seem like games written by people who haven’t observed kids playing RPGs in the wild. The most worrisome was Playground Adventures, which actually pitches itself as a game about making good moral decisions. Kids are amoral little psychopaths in games, and no RPG is going to reign that in. (I certainly haven’t in my four years of running RPGs with kids.)

Most kids’ RPGs are highly mission based. Set up a quest, have the kids go do it. Turns out that that kids love random tables and surprising twists that they have to deal with on the fly. Most Kids RPGs focus on carefully designed PCs who don’t ever die. Turns out that kids love the high-risk, high-reward structure of lethal dungeon crawls, and love generating oddball characters with dice rather than planning them out. Turns out that kids don’t enjoy games where violence is sanitized or glossed over, and enjoy dealing with real danger.

(Example: I had a game where kids were on a sinking ship in a storm. They piled into the lifeboat, but there wasn’t enough room for the captain, who begged to be put on board. One kid looked at the others and said. “It’s okay guys, the captain always goes down with his ship,” and they rowed away.)

The biggest problem is that these games talk down to their audience, and kids (at least 5th graders) can smell condescension a mile away. Kids don’t want to be “A Cool Robot that love Ooey-Gooey things,” as No Thank You Evil! would have you believe. They want to be Spike, A Chaotic Neutral Fire-dog Rogue with claws, fire fangs, and a 7d6 fireball spell.


Variable d6 weapon damage

Delilah by Barry Moser
Delilah by Barry Moser

I’m not a huge fan of the highly differentiated weapon damage in DnD. All weapons are deadly in the right situations, so the 2d6 of a longsword and the d4 of a dagger don’t make that much sense to me. On the other hand, OD&D, with its flat d6 for all weapons, doesn’t sit right either.

I’m working on a 2d6 system that’s a bit more robust than my previous Maze Rats, but still simple and fast to play. One of its conceits is that I’d like to use 2d6 for everything, including damage, and this ended up evolving into a very satisfying system that both differentiates weapons and prevents the swingyness of rolling a single damage die.

There are two types of weapons, heavy and light. Heavy weapons use two hands (so this includes bows) and light weapons use one. The advantage to using a light weapon is you can also hold a shield (dual wielding weapons strikes me as a bit silly). Shields can be splintered to negate all damage from 1 attack, as per Trollsmyth’s excellent idea.

When you hit with a heavy weapon, roll 2d6 and use the greater die. When you hit with a light weapon, use the lesser one. When you make a critical hit, add them together. Simple.

This results in much lower damage output than DnD, especially since armor absorbs damage (max 2), but that just means that HP totals are lower, which reduces bookkeeping. All weapons have the same max damage, but larger weapons are tilted towards the higher end, which fits with my ethos of “All weapons can be deadly.” Looking forward to how it work in play this Tuesday.

Maze Rats

Sam Bosma

I’ve spent the last few months polishing Maze Rats, a minimalistic OSR-style dungeon crawler derived from Chris McDowall’s Into the Odd, and which should appear soon in a supplement for that game, Odditional Material. I may expand it later into something more complete, but it’s perfectly playable as is now. It also fits onto two double sided sheets, making it ideal for players new to RPGs. You can make characters in minutes, and explain the rules just as quickly. Download the whole thing below and let me know what you think!

Maze Rats 0.1

Simplified Notches

Over the summer, I spent a lot of time reading up on OSR games, and gaining a new appreciation for that style of play. I’m working on a DnD mashup game called The Broken Throne that combines my favorite mechanics from earlier editions with house rules from DIY DND blogs round the web.

I’ll write a more in-depth post about that later, but today I want to look at one of my favorite mechanics, notches. I first heard of notches via Last Gasp Grimoire, but Logan’s system for tracking weapon and armor degradation is a bit too complicated for my taste, so I looked for a way to slim it down a bit.


My main complaint was that there were two values you had to track, quality and notches. In Logan’s system, rolling a weapon’s quality or less made you add notches equal to the quality, and from then on if you rolled quality or less you had to roll over notches on the weapon’s damage die or add another notch. Gaining notches equal to the damage die or failing to roll over the notches broke the weapon.

I tried a couple things, but the most straightforward solution was to eliminate the quality value and just use notches. Weapons start with 1-5 notches. If you roll notches or lower on an attack roll, try to roll over the notches on the damage die. If you successfully do this, add another notch. If not, the weapon breaks.

For armor, if you roll notches or lower on a defense roll (I use contested defense), add a notch and subtract 1 AC. Armor breaks at 0 AC.

This has a couple interesting effects. First, it makes it possible, though very unlikely, for high quality weapons to break on the first swing, which wasn’t possible in the original rules. Second, as weapons take damage the threshold at which you test for breakage rises. Thus, the breakdown escalates more quickly over time, rather than remaining static.

These rules are a bit harsher than Logan’s, but I’m willing to pay that price for simplicity.

Roleplaying Stats: The Four Humors

The subject of the classical four humors came up in my 5th grade class today. According to Galen, there were four fluids that controlled the personality: Black Bile, Yellow Bile, Phlegm, and Blood. The corresponding personality types were Melancholic, Choleric, Phlegmatic, and Sanguine, meaning “Sad and Thoughtful,” “Intense and Angry,” “Relaxed and Easy-Going” and “Outgoing and Sociable,” roughly speaking.

It might be interesting to use these as character stats, but translated into RPG terms. For example, Investigation, Aggression, Stealth, and Social. Presuming that the values for these stats would be distributed differently among the players, you’d have characters that would have to focus on very different play styles in order to succeed.