# What effects would using a d12 and adjusted TNs have on Dungeon World?

First of all I declare myself a crazy lover of the d12 die. I would like to know, if there will be a substantial difference if I change the bell curved 2d6 roll for a linear 1d12 roll. I did a little probabilistic testing on my own, by hand and using Anydice, and plan to change the fixed TNs and modifiers like this (percentages are with an unmodified roll):

• 10+ (16.6%) -> 11+ (16.6%)

• 7-9 (41.6%) -> 7-10 (33.3%)

• +1, +2, +3 -> +1, +3 +5; respectively, but also intermediate +2 and +4 will be present.

I'm also aware that I'll be adding more randomness to the results. But since I'm no mathematician myself, I'm worried there'll be something I'm not considering. So my question is, are other mechanical aspects of the system going to be substantially changed?

Since you already know and are fine with minor adjustments to probabilities I'll ignore those - but there are three bigger issues that need addressing:

This is probably the biggest problem. Many moves in Dungeon World grant the character an extra bonus for a roll of 12 or above. With 2d6, the probability is 1/36, 3/36, 6/36 or 10/36 for a bonus of +0, +1, +2 and +3 respectively (and impossible with a negative roll modifier). Rolling the maximum result of a d12 is significantly more probable than rolling the maximum result of 2d6 - you may need to get creative to keep the "critical hit" both possible at +0 and still reasonably unlikely to happen.

Some class moves (at least the Barbarian's Herculean Appetites) allow the player to roll a d6 and d8 instead of 2d6. In the Barbarian's case it is not just a question of a different distribution either, because the relative value of the dice matter - there is a complication if the d6's result is the greater of the two.

## What about roll bonuses greater than +3?

Best to have these planned out in advance, before someone with a +3 attribute modifier gets +1 ongoing! You can use AnyDice to find appropriate values for greater bonuses so they match your desired level of randomness.

• About the 12+: whenever you roll a 12 in a d12 you roll another d12. In a 9+ you the benefits of the crit, otherwise is treated like a 11+ (anydice.com/program/aa0a both have 2.78%). About the d8: a d6+d8 and d12+d2 both have a 25% of a partial success, but the later gives a 2% less chances to get a total success on a 11+. It will make the move too weak? Feb 5, 2017 at 16:20
• @Eldhrimer Which of the 12+ rolls get modifiers? Or do both? For the latter question, you'll need to figure a way to include the "backfire" of Herculean appetite. Feb 5, 2017 at 16:44
• Okay, I toyed with anydice trying to get a correlation. Please advice me if this is wheter too complicated or not. anydice.com/program/aa34 The modifiers are substracted from the trigger number for the reroll or explode. Then, the second die is subject to a TN of 9+. Example: You roll+WIS. Your wisdom modifier is a +2. So you take 2 from the base trigger number (12-2=10). If you roll 10+ on your first d12, then you roll again, against 9+. If you succed, with a chance of 10,42%, you take the advantage provided originally for a 12+. Feb 6, 2017 at 4:26
• I have not seen other moves such as Herculean Appetites. So I think I should just leave it unchanged. You make that move, instead of a d12 you roll d6+d8. Feb 6, 2017 at 4:29

If it's really about the dice, get a pair of these and play as written?

http://doublesix-dice.myshopify.com/ - d12s marked 1-6 twice.

That way you get the die you prefer, with no unforeseen changes to the game.

If you can't purchase doublesix dice (or their sister dice, triplefours), you can get the same thing with every gamer's favorite tool...arithmetic division! Just roll 2d12 and divide the sum by two, rounding the n.5 values up to the next integer.

You get to use the dice you like (which I understand, they roll nicely) without changing the game or making an expensive outlay.

• Though I like the idea, in the place I live is expensive and hard to find normal polyhedral dice. And shipping is currently largely unavailable. Feb 5, 2017 at 15:37

With the adjusted numbers you have, life will be significantly harder for characters. Dungeon World 7-9 (Success with complications) is 41.6% of outcomes, which you're mapping to d12 7-10, 33.3% of outcomes. You've increased the proportion of failures by one-twelfth, which would be noticeable in play.

Fortunately, this is easy to fix. Map DW 7-9 (41.6%) to d12 6-10 (41.6%). That matches DW probabilities.

• The problem with that is that when you get to the +5 attribute modifier, everything will be at least a partial success. There will be no chance for that player to fail those moves. Feb 5, 2017 at 15:35
• So don't have attribute modifiers that big? Feb 5, 2017 at 16:10
• The thing is, it's going to be harder at the low levels, but also they will improve more quickly, by failing more and marking more XP. At 1d12+5, they have the same chances as 2d6+3 for all the TNs. Feb 5, 2017 at 16:27
• Best of luck with that. Feb 5, 2017 at 16:39