After my initial thoughts about a core mechanic here and here, I think I’ve settled on a core mechanic.

I’m sorry d20, it was a close fight. Several commenters expressed their preference for a 2d10 where results further away from the mean become less and less likely. The range of values for 2d10 is still pretty wide, so there’s room for the very unlikely to still occur, but because of the 2d10 probability curve, results of die rolls won’t be quite so random and swingy as to overcome the skill of the parties involved.

Another nice feature of using 2d10 is that we can use two different colored dice. I can hang some mechanics off the differences between the two dice. For example, we could use a “light” die and a “dark” die representing various dualities of the world, and I can trigger certain powers or results based on a specific type of roll based on either the sum total of the dice, or the results of one die or the other. For example, a Paladin might have a power called “Holy Smite” that occurs on any hit where the “light” die rolls a 10.

You could get complicated with similar mechanics, but I don’t know if we’d need to. Some other examples of how you might use or trigger powers might be:

- Barbarian’s “Great Cleave” ignores armor damage reduction when the sum total of the dice are 18+
- Chaos Wizard’s “Chaos Bolt” strikes additional targets if one die is even and the other is odd.
- Monk’s “Bend like a Reed” power lets you add +2 to AC on any miss where the white die is 2 or less.
- An Archer’s “Precise Strike” lets you add the difference between the dice to the die roll result.
- A thief may take an immediate extra attack for sneak damage any time they roll “doubles” on an attack.

As for criticals, the base roll of a 10 on both dice would be a 1% chance, which makes critical hits pretty rare and far between. I’m thinking of a rule where a roll of a 10 on the white die always hits, and does damage equal to the black die. A roll of 10 on the black die automatically bypasses luck and fatigue damage (really wounding someone) as long as the result of the roll was actually a hit. A roll of 10 on both dice would bypass luck and fatigue, and probably deal extra wound damage as well, or maybe stun the person being hit.

I’ll need to run the math on such a rule and make sure that doesn’t make combat overly dangerous, but an automatic hit 1 in 10 helps prevent high defense from completely ruling the day, even if the result is a low amount of damage (presumably, the black die rolled low or else the result would have been a hit anyway). A result of a 10 on the black die will result in a critical hit only on a hit, so a low white die roll will still negate it, meaning we’re still looking at something between 5-10% chance to go straight to wound damage. We’re looking at a clear 1% chance of a true critical hit.

I also like that it’s different from the mainstays of Dungeons and Dragons and Pathfinder, as I think it’ll help me reinforce some different philosophy into the game since even the core mechanic has changed. Still, I’ll miss that d20…

wylliamjuddWhy do you want to create your own role playing game? What is it you want your game to do, that other games don’t already do? Or at least, what do you want your game to do better than the games that are already out there? Sometimes it seems like you’re just taking each element of D&D and adjusting it slightly. Why do that?

JackOfHeartsPost authorI think this is a good question. I tried to open by blog with an answer to that question, but it’s probably worth revisiting. Here was my initial answer to that question: https://lostworldsdesign.wordpress.com/2012/12/16/lost-worlds/

In summary, I’m doing it because I’m interested in game design and why different games have made different decisions, and what impact, if any, it has on the actual play of that game. Second, I know there are some themes I’d like to have in my RPG that I feel require a bit more redesign of an RPG than just tweaking 3.5 or 4e, or reverting back to a retro-clone.

wylliamjudd1 – I hope you didn’t take my previous comment as too critical.

2 – I do like this mechanic, and I think that it has a lot of potential.

3 – Am I the only person leaving comments who isn’t one of your gaming buddies?

4 – Is this blog intended for your gaming buddies, or for a broader audience?

JackOfHeartsPost author1. Of course not. I’m hoping that in the end I don’t have a “slightly modified” version of D&D, but honestly the game is fun and the various editions are the basis for the changes I want to make. If it feels like that to you, or the players, then so be it, as long as the changes I’ve made address the annoyances I have with the game.

2. Thanks, the more I’ve thought about it, the more I’m kind of excited by it. The only real concern I have with it is whether it will reduce the speed of the game by having to make the additions and check for triggers.

3. No, you’re not, although there are only a couple of people on here outside my group.

4. Initially, it was aimed at a generic audience, but I was hopeful to get a lot of feedback from my play group. I haven’t really made much attempt to publicize it, and it’s a place for me to write my thoughts and capture things that might have just been a thought that I’d lose if I didn’t write about it.

wylliamjuddI’ve been meaning to make a point about what this mechanic means mathematically. Here are some chances of success for comparison:

55% chance : 9+ on d20 : 11+ on 2d10

45% chance : 11+ on d20 : 12+ on 2d10

15% chance : 18+ on d20 : 16+ on 2d10

10% chance : 19+ on d20 : 17+ on 2d10

So what does this mean for game play? It does NOT mean more predictable chances. A 15% chance is a 15% chance, whether you need 18+ on a d20, or 16+ on 2d10.

What it does mean (for 2d10) is that as the difficulty value gets higher (from 11 on), the chance of success is affected less.

11+ : 55% chance

12+ : 45% chance

13+ : 36% chance

14+ : 28% chance

15+ : 21% chance

16+ : 15% chance

17+ : 10% chance

18+ : 6% chance

19+ : 3% chance

20+ : 1% chance

Conversely, it means that flat bonuses have an increasing affect on your chance of success. Let’s look at 15+ for example:

2d10 : 21% chance

2d10 +1 : 28% chance (+1 = +7% chance)

2d10 +2 : 36% chance (+2 = +15% chance)

2d10 +3 : 45% chance (+3 = +24% chance)

2d10 +4 : 55% chance (+4 = +34% chance)

(Actually, once you reach a 55% chance, the bonuses have a decreasing affect.)

When dealing with something like damage, an evening out of the average total helps to make the affects more predictable. However, this is not the case for chance of success. It merely varies the percentage jumps from one difficulty to another, and from a specific bonus to another. I’m not saying that this is a good or bad thing, it’s just something to be aware of.

wylliamjuddI made a mistake on that first comparison – it should be

55% chance : 10+ on d20 : 11+ on 2d10

45% chance : 12+ on d20 : 12+ on 2d10

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