Dice pool game design woes

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Well, that was fun
Staff member
those % are too high, there is no way one die has a 2% chance of exploding 5 times
I rounded up from 1.56%. This is what AnyDice shows me. I think I must be reading it wrong.

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Ravenous Bugblatter Beast of Traal
It looks like you are pretty far into this, but just for completeness another thought hit me I wanted to post. Specifically about the "lower number of dice have no chance".

What about two types of dice, a "standard" and a "risky". Standard is what you've suggested. (Or maybe four success sides, but that's a different discussion.)

Risky has two success sides, but all of the successes are criticals that count as two. And it a "AND..." side, which if rolled will amplify the results. What I mean by that is that if you fail the whole roll, it's "No, AND..." and you suffer some additional consequence. But if you succeed, it's "Yes, AND..." and you gain extra effect.

When rolling, players make up the die pool from their choice of the dice. So something they are going to have a good chance on will likely all be standard. Or maybe they will throw in one Risky looking for the AND. Ones they can't succeed at without additional successes but are doing anyhow will likely be all Risky. Ones where it's an okay but not great chance (the majority of rolls) will really depend on the player and the situation - which is good, that puts a meaningful choice in there.

With 3/6 successful sides, Standard would add 1/2 a success on average, and Risky would add 2/3 of a success on average, with a higher maximum successes but more chance of nothing.

With 4/6 successful sides, Standard would also add 2/3 chance of success, so the benefit of Risky is increasing the maximum (which isn't important in a boolean succeed/fail where you already can make it), but with increased consequences either way.


I think the problem needs to be tackled with a little lateral thinking, because changing the roll+bonus system into a dice pool really means changing the paradigm. It's not just a matter of arithmetic.

The advantage of using a pool is the immediate granularity of the results. Therefore, instead of establishing the number of successes required to satisfy a binary success/failure mechanism, I would use a fixed table that determines the quality of the action.
Number of HITS => Quality.
All '1' > Fumble
0 > Failure
1 > Failure or success with consequence
2 > Sufficient success
3 > Special success
On a single die you can aim for average to succeed poorly, which conforms to your character being poor in that area.
From the table above, decide for an average (look 4 is a good average).

The exploding die is "syntactic sugar", my players don't like it because it makes everything too unpredictable and simple. You can always hope for an extra HIT, which means having a lot of dice rewards even less. In fact, you have to consider that beyond a certain amount, adding more dice is less and less significant. With 6 exploding the gap between "poor" and "very good" is reduced even more. In my opinion, having limits helps to try more creative solutions.

The added advantage of the pool system is that you can easily adjust a lot of parameters, including the very way in which the player approaches the test, simulating "narrative" stuff. As an example, + 1 die if a personality trait conform to the action, convert a pool in a single "all in" die (simulating rush) or converting couple of dice into auto-hit (simulating carefull maneuvers). There's a lot one can figure out with a pool of dice, so reducing everything to % of success is very limiting.

As for the opposing actions, here too I suppose a paradigm shift is needed. Passive value roll is perfect for systems where you battle frequently and where you have a primary currency (HP) that gets eroded by context. You want thousand combat rolls and Saving Throws to be lightning fast, so you get back to what matters (choices and using wildcards).
I think a dice pool system should instead use opposing rolls, obviously trying to rationalize them. Subtract the higher HITs amount from the minor ones and determine the quality of the result. Increasing penalties for many defences in the round. A round-based death spiral. This slows down the combat phases, but it's not automatically a bad thing: the setting determines whether this part of the game should repeat itself often or not and being abstract or detailed.
So, in the end - to me is not just a matter of core mechanics, but of yours aggregated methods.
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I rounded up from 1.56%. This is what AnyDice shows me. I think I must be reading it wrong.

View attachment 283646
Forgive me if I've totally gotten this wrong, but if I understand, when using a d6, the definition of exploding means you roll a 6, right?

So in order to get 5 exploding dice, you need to roll 5 sixes in a row, is that correct? And that would be defined as 6*6*6*6*6, or 1 in 7,776 chance.


Forgive me if I've totally gotten this wrong, but if I understand, when using a d6, the definition of exploding means you roll a 6, right?

So in order to get 5 exploding dice, you need to roll 5 sixes in a row, is that correct? And that would be defined as 6*6*6*6*6, or 1 in 7,776 chance.
yes, hence the chance for one die to meet a target of 6 is (1/6)^5 / 2 (the /2 because there is a 50% chance the last roll scores one point), or 0.00643% chance of this.

I have no idea what the percentages shown represent, but certainly not this.


I am having the darnedest time finding the free basic rules. Do you have a link?
Apologies, I wasn't precise - the data is spread over a few freely available downloads.

Start with Creator's Kit:

Then head to Slayers by Gila RPGs, scroll down to Rules reference and character sheets. Between the two you get everything besides character creation and hunt design.

Go to
Slayers Third Party Content - Collection by Gila RPGs for third party content, some of which is pay what you want.

Good luck.


Well, that was fun
Staff member
So I found somebody asking a similar question which led me to another AnyDice script.

Now, assuming I'm reading this one correctly we have:

1 die50%8.33%1.39%0.23%0.04%0.01%
2 dice75%33.33%9.03%2.08%0.44%0.09%
3 dice87.5%56.25%25%8.22%2.29%0.57%
4 dice93.75%72.92%43.4%19.68%7.16%2.24%
5 dice96.88%83.85%59.98%34.30%15.86%6.15%
6 dice98.44%90.63%73.05%49.32%27.58%12.96%

The numbers of the single die still don't look right to me though. Quick calculations using a spreadsheet for the odds of numbers of explosions:

# of explosions neededis 1 in....as a %
1 (TN 2)616.66666667
2 (TN 3)362.777777778
3 (TN 4)2160.462962963
4 (TN 5)12960.07716049383
5 (TN 6)77760.0128600823

So it's still not right. And if the single die row is wrong, they probably all are.

Hang on, I'm not counting the final die as not needing to explode and so it's 1/2 for a success not 1/6 for an explosion on that one. Dammit my head hurts!
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Well, that was fun
Staff member
For one die the following results are a hit on TN 6 (focusing on that number as it's the extreme one):


All of those are a hit. 5 explosions then 50% on the final die. Whip out a spreadsheet and work it through...

1 in1 in1 in%
TNbase chance# explosions neededchance of those explosionsand then 50% final rollas a %

Aha! These are the same numbers as in the AnyDice chart in my last post. Which means I think that chart is actually correct!


Prince Valiant has a rule that if all the dice are successes, an additional success.

The Burning Wheel family of games have various rules which make 6s "open ended" ie each 6 adds another die to the pool, which is also open-ended.

Calculating the odds for open-ended dice is a bit tricky for the reasons @Thomas Shey gives, but some rough noodling around is possible.

Eg with 3D, the probability of no sixes is 5/6 cubed, so the probability of at least 1 six, ie actually counting as a pool of 4D+, is 91/216, or not much short of half. So it is a meaningful change to the possible range of outcomes.
This calculates 6s adding an additional die.

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