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D&D 5E Introducing the COUNTDOWN DICE Mechanic!


Another thought, you could add a mechanic for characters to push their luck by willfully removing a die from the pool in return for some beneficial effect - a hint, advantage on a roll, rerolling damage, acquisition of a tangentially beneficial item, etc.

Furthermore, you can also use gradiants of the pool. For example, if the entire dungeon will collapse when the Countdown pool is exhausted, it could be that after a certain number of dice are lost, non-essential sections of the dungeon may collapse. For example, a bonus treasure room might become inaccessible after 4 dice are lost, the "short" route may become unavailable after 6 dice are lost and when 8 dice are lost sections of the main route fall away, requiring the characters to parkour, fly or otherwise get creative to make it out. When all 10 dice are gone, the whole thing falls away...

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It is also called exponential decay. We use that to simulate radioactivity (I don't know all the correct English words).

The average remaining dice can be calculated with the formula:

Remaining-dice = Starting-number-of-dice * (5/6)^turns

Note, that with this formula you will never approach zero, as it uses a continuum instead of discrete numbers.

You can use the formula for the half-life-time and say: after 10 half-life times you are close to zero.

You can also use a treshold and say: if you get below < 0.5 you are done and use logarithm to estimate the rounds.

You can probably just look up a formula on the internet too. ;)

Your encouragement to just think about it got me to pull my head out of my tookus.

Realizing it's the largest order statistic of a geometric distribution does certainly make it easier! Here's (some not too pretty) code for looking up to turnmax turns and using a dice with nsides. This replaces the code in post #8 above.


for (i in 1:turnmax){
if (i==1){pendon<-pendby[ i]}
else{pendon[ i]<-pendby[ i]-pendby[ i-1]}}

x<-cbind(1 : (turnmax+1),round(pendon,4),round(pendby,4))
colnames(x)<-c("turn #","on that turn","by that turn")
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I think these are the results for mean and sd of number of turns using one to ten d4:

ndice mean standard deviation
[1,] 4.000000 3.464102
[2,] 5.714286 3.896623
[3,] 6.872587 4.065951
[4,] 7.741776 4.157531
[5,] 8.437008 4.215216
[6,] 9.016347 4.254849
[7,] 9.512926 4.283732
[8,] 9.947433 4.305713
[9,] 10.333662 4.323000
[10,] 10.681268 4.336953
Yup, I get the same values.

In general, larger numbers of smaller dice will yield more consistent results. (9d4 and 3d6 have roughly the same average duration, but you're far less likely to see your countdown expire on the first round with 9d4.)

If you want to ensure an absolute minimum duration, you can put a cap on the number of dice that can be removed from the pool each round.

I'd also suggest having dice exit the pool on a roll of 1 rather than 6*. This has no effect on the probabilities, but in most of the scenarios I can imagine for this mechanic, the players are racing the clock; so tick-down on 1 is consistent with "low numbers are bad." It also means you can use any size die, or even a mix of dice, without having to think about what number you're looking for.

*Or 4, or whatever size die you're using.
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I like using a similar method. A pool of d6s that is rolled after each time interval. If all the dice are 6s the time expires. If you roll and all the dice aren't sixes you reduce the dice pool by 1 to a minimum of 1. Dice can be added or subtracted by the actions taken by the players. Actions taken by npcs can force another roll.

I like it because the pool shrinks at a steady rate, giving a sense of growing dread to the players. The odds of getting all 6s prior to 2 dice is also really low* so when the pool has 5 dice the players are confident they have at least 5 intervals to achieve success. On the flip side sometimes I'll roll in between intervals due to something happening outside the view of the players (think wandering enemies). Or because of something in view (priest accelerates the ritual instead of casting a spell at the players). This can really light a fire under the butts of players.

Could also do something similar by using shinking die sizes rather than removing dice (or combine the two).

Can work with fewer dice and provides a bit more control over the possibility that you yahtzee your doom clock.


I have used this heavily in my current A5e game and have found it an excellent mechanic. I have often used it for threats over long period of time. For example, my current game involves a number of fey lords. Because their sense of time is very capricious, their activities are often random in time. Recently the party greatly angered one of them, so I set up a doom clock for retaliation. The fey lord is coming, but will it be next week....or 3 months from now? The clock adds that fun tension.

I also like the countdown clock combined with A5e's "Doomed Condition". Doomed is a status condition where the person is going to die, and simple "clerical healing" is not sufficient to save them. Now the core condition is "this person is going to die, no matter what" but what I have found more effective in my game is to add some plot way to save them, and attach a doom clock.

So the party must get the magical flower X to save this person, and the doom clock triggers once every day. Will the party get back in time to save the person.....we will find out!
It seems like a good way to handle poisoning as well. You are stricken with a deadly poison (how deadly determines the number of dice) and you roll each morning to determine your fate. In addition to a cure, there can be methods to add or subtract dice to the pool.


An additional idea for holding breath, overland travel, etc.

Take a number of D6's equal to your Con, and roll them at each interval (rounds, minutes, 10 minutes, half-hour, hour as appropriate). As normal each 1 is removed from the pool. If you exert yourself in some way, you automatically remove a die as well.

So, if for example, someone was holding their breath underwater and had a Con of 10, you'd roll 10 dice every round, removing 1's from each roll. If the character was also fighting, each round you'd reduce the pool by one die, in addition to the 1's being rolled.

Another example, the party is travelling from point A to B. Using the lowest Con of the party's members, you make a roll every half hour. When the party runs out of dice, they need to stop and rest (levels of exhaustion if they don't). If they have an encounter or do a force march to increase their travel rate by 50%, they remove a die from the pool. If they stop to take a short rest, they can add a die back to the pool.

You could also use a double-edged pool for a chase. Start with a number of dice, say 10. Every time a 1 is rolled, the target(s) gets further away. Every time a 6 is rolled, the party gets closer to catching their target. Each side can perform one trick or stunt to attempt to remove a die in their favor - The party's Ranger successfully making a skill check to track the enemy counts a die as a 6. The enemy successfully using Stealth to hide in an alley counts the die as a 1. And so on.
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