d10 Core – Second Edition planned

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After looking over the d10 Core Roleplaying Game System after being released, and with the feedback of many, many people, I have decided to go ahead and move into the second edition without further delay.

This decision was based on several factors, such as loopholes in rules, items needing clarification, some definitions, and problems with the dice mechanics.  Many people that read over the entire book didn’t quite understand how things were suppose to work, so, some things are staying the same in second edition, but many things are going to change, and some things are going to be completely redesigned.

For those interested, the key changes are listed below.  This is a planned change list, though; the items on this list will be changed, but there may very well be more changes than this coming.

Dice Mechanics Completely Changed

When considering how dice mechanics operated in first edition, I felt a bit dry.  It followed the same old die + stat mod + skill mod = roll mold.  I agree with people who felt a little dry about the mechanic – it’s a sturdy mechanic and does the job just fine, but it’s been used so much that doesn’t give d10 Core a real edge by using that mechanic.

Instead of the above, I thought very long and hard about a mechanic that still used the d10 (as I prefer it to larger and smaller die types, it just seems like a very balanced polyhedron to me), has depth, is exciting, and has not really been done before (or, at least hasn’t been overdone to the point of the original formula).  I labored my brain for a week, thinking of what had been done before, and trying to make the dice system unique (or at least very rare if someone has done it before).

I thought about Unisystem.  I thought about d20 system.  I thought about Storyteller and Trinity.  I read articles about dice mechanics, probability systems, and the like.  I also read a particular probability article about the Axis & Allies board game (which I enjoyed when I could find people brave enough to face me).  This article linked to another article about dice probabilities in the board game Risk, which I also greatly enjoyed when I could find brave souls to face off for a night of world conquest.

I read over the Wikipedia article, and the game was afoot.

In short, the board game Risk has a rather simple dice mechanic based on the six-sided dice, d6s.  If you attack and commit three or more armies, you can roll three dice, while the defender can roll a maximum of two dice if he has two or more armies, and one die if he has one army left.  If you attack with two armies, you can roll two dice, and one die if you attack with one army.

This is a by-die comparison battle, meaning that the highest die you roll is compared against the enemy’s highest die, and so on until each die has been resolved.  It determines who wins the mini-battle, and how much damage is inflicted.  For instance, if I attack with 3 armies in Risk against 2 armies, I roll 3d6 and the enemy rolls 2d6.  I receive a 6, 4, and 3 as my rolls.  The enemy receives a 5 and a 4.  Since 6 > 5, and the 4s match exactly, we each lose one army (since the rules state the defender wins in the event of a tie).  My 6 beat the enemy’s 5 (one army lost for him), but the 4s tied (one army lost for me).  The battle continues until one player withdraws or is completely destroyed.

I started thinking about how the die comparison model could work in a roleplaying game, and my first answers were fraught with great difficulties.  For instance, the rules of Risk are vastly simplified to make battles quick, but the games can go on for days, weeks, and in some cases months.  The die comparison model would have to be adjusted to work for a roleplaying system.

First, I thought about using a d10 for resolution.  How could tasks be resolved?  White Wolf‘s Storyteller system uses a modified die comparison model:  players roll a number of dice equal to their attribute and ability combined against a target number that the game master decides.  One thing people didn’t like about d10 Core was the arbitrary decision of target numbers to resolve a task.  It gave guidelines, but, similarly to White Wolf’s system, it was up to the game master to decide how hard a task really was, and that sometimes made things impossible to accomplish.

Since I’m scrapping the game master’s decision factor in task targets, I needed something else.  I don’t want to make huge charts of task targets for different tasks (ala D&D) because I think they’re largely ignored by casual roleplayers, and they require even more book flipping during the session, I’ve decided to go with a different approach.

Using a die comparison like risk, where the source of a task check and the target are both dynamic, it takes a lot of the pressure off of the game master.  He would, instead, decide how many dice the task is worth instead of coming up with a specific target.  The dice are randomly rolled, giving a random chance of how important a task is at that specific time.

Instead of the game master saying, “That’s really hard, given the circumstances.  Roll at target 9”, the game master says “That’s usually pretty hard, given the circumstances.  Task is 5 dice.”  The player rolls his dice, let’s say 4 dice, and the game master rolls 5 dice.  Though the probability is against the player, he still has a good chance to win.  The game master rolled 9, 8, 5, 4, 1, and the player rolled 10, 10, 8, 5.  The match-up is 10>9, 10>8, 8>5, 5>4, so the player has 4 “hits”.  (Ones are thrown out since they serve no purpose in the mechanics, it will always be beaten by anything other than a one, and matches cancel themselves out.)

The player has 4 wins.  So, he has won with a large margin against a task that was harder than his capabilities.  The game master judged the task as being “pretty hard”, but only assigns dice as the task difficulty instead of a hard number the player must beat.  This allows players a real chance to succeed, even at tasks that seem impossible, because they have a chance of beating the task dice, instead of some outrageously-high number that represents difficulty.

I have included two charts for reference in this matter of die probabilities.  The first chart describes the relationship between a player rolling 3, 5, 7, or 10 dice, and receiving at least two of the X-axis results or higher.  Basically, the results above the 50% line indicate how many times they can expect the X-axis number to return based on how many dice they roll.  The first chart requires at least two dice to return the X-axis number or higher:

Die Probability Chart

Illustrating probability of getting at least two of the number to return on dice in a single roll.

The above chart indicates the kind of chances a player will have to do well.  The player with more dice receives an advantage, but the disparity between each tier of dice level is not overwhelming, and they all perform within a 30% rate at the top end (which is not impossible to achieve, even for a player rolling 3 dice against 10).

The next chart describes the relationship of 3, 5, 7, and 10 dice all rolling at least 3 results of the X-axis number on the die.  As expected, players rolling more dice do much better, even at the 5-dice tier, than the player rolling 3 dice.  This is because the player rolling 3 dice must match all three dice, while players who have more dice have more chances to match at least 3 of theirs to the result.

Die Probability Chart

Illustrating probability of getting at least three of the number to return on dice in a single roll.

The player with 3 dice performs considerably worse than the others when the roll becomes much harder, while someone rolling 5 dice against 10 still has a fighting chance, and the player rolling 7 dice against 10 doesn’t feel automatically defeated by any means.

This single change completely changes the way the game is played, and it also makes it much easier to streamline the rest of the mechanics.  Instead of huge charts of task targets or a couple of paragraphs explaining how to make up a task target, the difficulty mechanic will have guidelines of how to add or remove dice from a task pool and explain why it is easier and less argumentative to do it this way.

In addition, players would be less likely to complain about an extra die or two in difficulty change as opposed to a few points in a task target change.

Combining everything into a single roll

Since the mechanic has been changed to this dice comparison model, I also thought about how damage needs to be rolled (for combat situations) or how degrees of success can yield different results.  There were two options available:  the old way (roll damage/degrees separately) or the new way (roll one time, and let that roll also determine damage/degrees of success).  I went with the new way.

Using the example from above, the player had 4 “hits” since he beat the game master 4 times, and the game master didn’t have any “hits” of his own to cancel out any of the player’s “hits”.

In a combat situation, this could easily be applied directly to an enemy as damage.  Player “hit” four times, take 4 hits on your hit points.  In a non-combat situation, this could be applied to the result of a task check.  If it were a search check, for instance, the game master could say “You found the hair pin that you were looking for, but you did so well that you found a man’s shoe under the couch, indicating that it was a male who committed the crime instead of a female like everyone told you earlier.”

This does two things:  fast dice resolution of tasks and easy handling of degrees of success.  I like it.

Keeping the dice under control

There also has to be considerations for keeping the dice under control.  For instance, the player has enough stats, skills, and other benefits that add dice to his pool that it goes into ridiculous proportions.  Although it would be epic to have people throwing 25 dice across the room, half of them falling off the table, some landing in drinks, and so forth, a rule needs to be in place to keep things reasonable.

I have three ideas on this.  The first is the rule, the second and third are optional add-ons.

Reserve above 10 – this rule declares that a player may roll a maximum of ten dice for any task.  This also makes the game master’s max dice pool at 10 to keep things fair.  Ten dice is enough to be epic, but not so ridiculous as to find dice under the couch and in the refrigerator a week later.  Anything above ten still counts as dice pool for purposes of effects the reduce the player’s dice, but they are not rolled.

Use Reserve to Re-roll Ones – since ones are discarded, an optional add-on rule is that a player can pull from his reserves to re-roll any ones that come up, giving him a chance to get more hits in a big fight or a high-level task.  The game master is also allowed this option if the task or enemy has reserve dice.

Reserves Hit Automatically – since the player has so much talent or so much in his favor, any dice above ten count as automatic hits. If the player has effects that reduce his dice pool, the reduction is made against reserve dice first.  This may be included as part of special training and powers only, to give them a boosted benefit.

Time management & Movement rules

In the original system, some were complaining about how time is not clearly defined.  While this is fine for more casual groups, it may not be the best for the mainstream.  Additionally, movement is not clearly defined, so these two problems will be addressed.

I have tried to consider time management and what would be the best.  I am thinking of using two different time management systems, one for “small scale/tactical/time sensitive” and another for “large scale/strategic/time insensitive”.  Probably 6 seconds on the small scale, and maybe even up to a minute on the large scale, with rules for entering and leaving “strategic” and “tactical” combat.  Either way, they must be uniform to convert from one to another easily, so 6 seconds and either 30 seconds or 1 minute for strategic rounds may be best.


I feel a bit more excited about compiling a dice mechanic that I really like, that’s easy to use, requires only the simplest math (and single-digit numbers in the equations), and it not commonly in use in any other RPG system presently that I’m aware of.  If it is in use already, I haven’t heard of it, which should be a good thing.

Hopefully, I can get a little feedback on these ideas to see if it’s totally absurd, or if it makes decent sense to others.  For now, I’m off!


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  1. Myles Milner  July 9, 2013

    I like the dice mechanic you presented here. I had a similar idea to use the risk system and try to stick with D6’s but the probability curve was not steep enough for wider ranged rolls as you so eloquently pointed out in other posts. But the Risk match up system was a good one and I did not want it to go to waist. I moved to D10’s with a bit of variance on skill checks that are not versus another character, enemy, or NPC, instituting a general chaos rule where the task dice the player is matched up with is at a set minus amount from the skill value. This way the Game Master must only make decisions on skill check dice pools that are above the players expertise. I appreciate all you have done with D10 and I am looking forward to play testing my game with your system.


    • Brian  July 21, 2013

      Thank you, and sorry it took a bit to get back to you. We’ve had some big changes going on here lately.

      In respect to dice comparison, I may move away from the direct comparison because it does have one major flaw: the inability for everyone to roll for something without things getting a little clunky. The favored mechanic right now is rolling for matches and then comparing the result against an opposing dice pool. For instance:

      Player 1 rolls 10, 9, 9, 7, 5 (2 dice match. +2 hits)
      Player 2 rolls 7, 7, 6, 6, 2 (2 dice match in two sets. +4 hits)

      +4 hits – (+2 hits) = +2 hits in the favor of Player 2. Player 2 succeeds by two degrees (or deals +2 damage to Player 1, or whatever the task resolves to).

      It would allow an unlimited number of comparison in a quick way. In the original method, direct comparison, you run into a problem where you have to compare each pool’s raw results to every other pool on the board. The new favored mechanic allows a couple of things that most systems don’t: all numbers become useful, and there is no “automatic win” roll, like there is in d20 system (for instance). I’ve played in several games where a person rolls a 17 or higher and automatically assumes it will work. Likewise, people say “I failed” instead of adding up numbers when they roll very low, even if they might have succeeded.

      And thank you for visiting, too. 🙂 I always enjoy having visitors. I am also working on launching d10core.com to house the system’s information and news, but since my server crashed last month, I’ve just been busy getting everything I already have back online.

  2. Myles Milner  December 14, 2013

    Brian, I wanted to thank you for giving me help with understanding your dice mechanic. I have been developing an RPG for the better part of a year and I wanted a dice mechanic that was not a D20 based setup. I will be play testing with two groups in the DC area to work out the bug starting in January.

    • Brian  December 16, 2013

      Thank you. 🙂 Yes, I know how these things can drag on and on. I’ve been working on this system and playing with mechanics and rules for probably five years altogether now.

      And if you are using a similar mechanic to the one described above, I’d love to hear about your testing results. It’s difficult for me to get a group together to test in my area; if anything, I’m fortunate to play one of the mainstream systems at all. 🙂

  3. Myles Milner  June 13, 2014


    It has been some time since my last correspondence and in the interim, my RPG group has performed two play tests with a third coming in July. I want to tell you how things are going but for it to make sense I will give you a bit of context as to how I have implemented your system. I am running five base attributes that are connected to a robust battery of skills used for role play and combat encounters. The value of any skill determines how many d10’s you will roll to resolve a challenge. The skills are augmented by gear and merits (very similar to feats in D&D). Since the starting attributes of each character are no higher than a two, the most d10’s my players are rolling are 4 as a basis but receive bonus dice during combat for special situations. It works well and is fair based on the fact that there is always an opposing dice roll of similar or equal amount just as you had explained in your first reply. We did however apply a few tweaks that might interest you.

    1. During a dice roll when both rolls contains the same amount of dice, we compare the highest non-matching die to resolve the tie. If those two dice are the same then an additional 1d10 is rolled until one die is greater than the other. While this does effect overall probability due to comparison and additional die rolls, the players have all agreed that they are given a fighting chance to be successful if even by a slim margin.

    2. Critical Success for dice rolls are classified as a dice roll that contains no non-matching dice. In combat, I consider this to be a Critical Hit or Critical Defense giving the player special bonuses to immediate future dice rolls. For a skill check, the player benefit is additional information or bonuses to subsequent skill check of a similar nature. The opposing roll getting a Critical Success during a skill check is seen as a critical failure for the player putting them at a clear disadvantage. I am still tweaking the outcome of a Critical Success on both dice rolls.

    3. Successive winning dice rolls was a nice afterthought I added due to the fact that always dealing with an opposing roll puts the possibility of success in a greater state of flux. To make it worth a players while during combat anytime a player is able to be win in three consecutive dice rolls, they are able to glean a benefit from it but not as great as a Critical Success.

    4. Calculating damage in combat is collected from the dice roll as well. The basis of damage dealt by a character is adding the skill value + any gear bonuses + any merit bonuses + the standard damage bonus of the weapon being used. If the player wins the dice roll they add the matches rolled to their damage base so overtime, the player will deal more damage at higher levels.

    There is much more detail to get into but I want to just focus on the place where the dice mechanic made the greatest impact and allowed for tweaking that did not break the game system. Overall I like it an I am definitely adopting the 10d10 dice roll cap and treat any overage as re-rolls for non matching dice since the only thing that matters is the amount of matches in a roll. Thanks for letting me play test with my group as I can see its benefits for future gaming projects. On a side note, do you plan on continuing with the second edition of D10 Core?


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