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DM of the Rings CXX:
Luck Thief

By Shamus
on Monday Jul 2, 2007
Filed under:
DM of the Rings


Gimli is stealing Aragorn’s luck.
Legolas points out their mistake.

The Truth About 20-Sided Dice:

There are a limited number of “twenties” in any given d20. That is, no matter how many times you roll a d20, you cannot roll another twenty once the supply has run out. These twenties can only be replenished by rolling a corresponding one with the same die. Thus every gamer is duty-bound to protect their supply of good rolls. If a friend rolls a twenty using your die, not only have they stolen your good roll, but they have doomed you to the extra one required to replenish the twenty.

Some players get excited when they roll several twenties in a row, concluding the dice are “hot”. Don’t make this blunder! This is like driving your car for 400 miles without gassing up, and then concluding that your car is a perpetual motion machine. After a few good rolls, pass the die off to an unwitting companion and let them charge it up for you.

Statisticians have known about this behavior for years. They call it “the probability seesaw”. Unlike the bell-shaped curve, in the seesaw system the odds of rolling high or low is directly proportional to what has been rolled in the past. They usually pretend this isn’t true. If a statistician hands you a die insisting that “any given roll has the same odds of rolling a one or a twenty”, it means he’s handing you a depleted die in the hopes of taking advantage of you. Don’t fall for it!

Now the secret is yours. Please put this knowledge to good use*.

*By “good use” I mean, “take advantage of other players”.

Comments (217)

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  1. Shawn says:

    I am sorry, the best thing about this particular one is the Babylon 5 reference :)

    My obsessions definitely have a pecking order… and a pack of Shadows or Vorlons dominate just about anything else… (except of course, for the Host of Valar! (And I will be forever bitter over the fact that, “Of the march of the host of the Valor to the north of Midle-Earth little is said in any tail…” WHY THE HECK IS THAT?!!?!?!?! Morgoth defeated, all Beleriand destroyed…. good stories I would think!! GRRRRR!)) <— Note that as a good coder, my parens ARE balanced!

  2. dlantoub says:

    I utterly subscribe to this theory about dice. However I protect my dice whether or not they roll good or bad. I was the only DnD fighter I met to have 4 hitpoints and a full set of field plate at level 2. i was also the most unluckily luckiest character in the game. In spite of weird random bonuses the GM gave me 90% of the time my character would miss completely in any type of combat. however the occasional 10% saw me roll near to maximum damage on every hit.

  3. Moridin says:

    It tells a lot about gamers that this specific discussion is the first(and probably the only) on to reach almost 200 replies. They are also, for the most part, wrong. The key to rolling high is to not to look, even glance, the die before it stops rolling when the roll is important. That way the die believes that the roll wasn’t important and will roll good.

  4. Andrew Jensen says:

    Some times probability doesn’t work. Onesesion of mine, a player rolled 3 20sin a row with the samedie Then other players proeded to roll about six more twenties with the die over that hour. The lowest number rolled was I believe a 5…

    And come on, reach 200 posts!

  5. Andrew Jensen says:

    ARGH! It screwed up and I wasn’t able to edit my post for the abundant typing errors!

  6. Robin says:

    The purpose of dice is to give an unpredictable result. You bought them specifically so you would have no control over the result. The game uses them precisely to give you no control over the result. That’s why there is so much effort spent trying to control the result.

    Having said that, here’s my take on why your dice hate you.

    Dice are pedantic mathematicians, and if you want to them to treat you well, then treat them well.

    1. One die; two dice. Never anger them by referring to a singular dice or plural die.

    2. Proper dice have opposite sides that add up to n+1. If the opposites sides of your die don’t add up to the same number, then they are not proper dice, and cannot be trusted. Wrap them up in fancy paper and give them to some kid you don’t like.

    3. It’s not a twelve-sider, it’s a dodecahedron. Once you’ve made friends with it, you may get less formal and call it a d12. But it’s still not a twelve-sider.

    4. Use correct plurals. They are not polyhedrons (tetrahedrons, octahedrons, etc.); they are polyhedra (tetrahedra, octahedra, etc.) How can you expect them to give you high numbers if they know you can’t handle numbers larger than one?

    5. Don’t mix dice from different manufacturers. If you put Koplow dice and Gamescience dice in the same bag, the Koplow dice get envious and the Gamescience dice get insulted. They can tell the difference.

    6. The five basic dice (tetrahedron, cube, octahedron, dodecahedron and icosahedron) are Platonic solids, or regular polyhedra. Many new dice out are Catalan solids (the d24, d30). Any die whose faces all meet at two unique points (d10, d16), whose faces aren’t all the same shape (d5, d7) or which isn’t a polyhedron (d100, d3), should be kept in a separate bag. The Platonic and Catalan solids know that these upstarts aren’t “real” dice.

    Oh, and Dave, about your d20 that never rolls higher than a six? The problem is that this die is a cube. (Last week, I had a player upset that he was rolling low numbers. I eventually noticed that he was rolling attack rolls with a d12.)

  7. BattlingDragon says:

    Before any game session, I will line my D20 up, 19’s up. I’ve noticed that when you roll, you usually miss your training point by 1. If you train for 20, you get either 19 or 1. By training to 19, I usually get 18 or 20. I will also roll all of them just before play begins and use the one that rolls highest until it rolls below 10. After that, I re-roll the remaining dice and send in the highest.

  8. BattlingDragon says:

    Sorry for the double post, but I couldn’t resist.


  9. Friedenmann says:

    Rolling a 20 tactics? This is just silly. The roll is bound to be random, unless the die isn’t well-balanced.

    In my experience there’s often a rule “the DM makes all rolls”, to avoid people arguing with him/her as to why somebody didn’t succeed when they have rolled a high number. If such rule exists people may went on talking about the DM cheating with their rolls or having unlucky throws, but they can’t do anything about it. Having the players fight over dice and arguing who sabotaged their throw with a mean look is worse than that, I guess.

  10. Rev says:

    After lurking so far I finally decided to comment; Thank you- It was a great day when I found this strip. love the “I need to make a diplomacy roll” line

  11. […] Truth About Dice: There are a limited number of “twenties” in any given d20.  That is, no […]

  12. Caradoc says:

    If anyone is still reading this preposterously long thread, I thought I’d tell a little story about dice rolls. I am usually a quite rational person and I understand frequency distributions, but my own sort of ‘luck’ seems a bit off kilter. My die rolls in D&D (and everything else, it seems, that involve random sequences) are consistently long stretches of bad to middling numbers, punctuated by lunatic runs of good ones.

    One I’ll never forget came when rolling up a character in Runequest or some other early system. Rolling percent dice for my character’s race, I hit 00 which sent me off to some ‘unusual race’ table. Another 00 sent me to a ‘monster’ table, and then a final 00 landed me in a ‘gods and demons’ table. A 97 there made me a Balrog. Hoo boy.

  13. Aeon_the_Hermit says:

    I have a chant that seems to replenish dice. it goes:
    “My dice are all rolling ones”

  14. Rob #2 says:

    Rule of First Posts: “First-Posters” should be kicked in the junk and banned from reading the next comic.

    Unless it was done in a way that everyone finds funny. Then all is forgiven and the poster is given encouragement.

  15. Saphroneth says:

    That is a really nice screencap in the penultimate panel. If it’s edited, it’s a masterful job – and if not, very good eye.

  16. Thom says:

    YAY Story time again! So my group is now playing Dark Heresy (fun game :D) which has open-ended damage. Invariably you roll max damage, then confirm that you can continue to roll, but your second die always, ALWAYS turns up “1”

  17. […] points us to an alternate dice theory, and provides us with a beer nutrition information […]

  18. Spike says:

    “What do you want, woman?!?!” this is excelent!

  19. Arkanabar says:

    I accumulated dice for a decade or more, and then decided to prune them down. I kept the ones with warm colors — a Chessex Fire set, some Chessex Strawberry (though I painted the green numbers gold), a pack of five red & white D6s that we’d bought back in the 80s, an early yellow-orange high impact d20 that was numbered 0-9 twice, that I colored half of with a sharpie to tell 1-10 from 11-20, some others in varying shades of red, orange, yellow, and/or black. They were AWESOME. They were so awesome, that I unintentionally came very close to TPK when running games a number of times. I called them my “Hot” set.

    So I built up a second set — a Chessex Water set of 7, supplemented with many 12mm Water d6s bought for Shadowrun, some solid blue d6s with white pips (and really awful quality control), four Chessex blue-and-maroon full sized d6s with silver spots, and some Barracudas (blue with black specks and gold numbers), and an extra Chessex “Cobalt” d20. They roll randomly. I call them my “cool” set.

    One day I accidentally left my backpack behind sitting in a common area at college. When I returned, the ONLY thing missing was my Hot dice set. I miss them still.

  20. WJS says:

    It’s true you know. If a die rolls low, it will probably do better next time. Conversely, if it rolls high, it probably won’t do so well next time.

    Seriously though, I just want to point out that you only get a bell curve if you’re rolling 3 dice or more. If you roll just one die, it’s a flat or uniform distribution, and if you roll two it’s a triangular distribution. 3+ and it starts to approach a proper bell-shaped normal distribution.

  21. I Art Laughing says:

    Or just file off the edges leading to the 20, round off the edges on the opposite side of the one and crisp up the edges opposite the 20.

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2 Trackbacks

  1. By Mimeti.ca » No Dice on Tuesday Sep 22, 2009 at 10:10 pm

    […] Truth About Dice: There are a limited number of “twenties” in any given d20.  That is, no […]

  2. […] points us to an alternate dice theory, and provides us with a beer nutrition information […]

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