HD&D: Core Concepts

In my last post I mentioned my general dissatisfaction with fourth edition, and my desire to create something that was better. Thanks for all the responses so far. Now, I’ve been thinking about this for a little while, and I have the bare bones of a solution which I begin to present to you in this post.

I wondered how best to present this information, and in the end I decided upon a virtual book. Imagine the PHB, DMG and MM and a goodly proportion of splat books are combined into one massive tome. I’ll take you through that tome chapter by chapter, and comment on how I think the rules in each section should work. Think of these rules as the starting point for an extended discussion. Nothing is set in stone at this stage.

This post looks at the first two virtual chapters: the core concepts and Iourn. Successive posts will cover the rest of the game.

I need to add one disclaimer before we begin. I am creating Hybrid D&D for the benefit of my campaigns. The system will be tailored to the way I run the game, and my players play the game. That will be its strength, but it will also be a weakness. The system won’t be designed as a one-size-fits-all game that is equally adept at political skullduggery and dunegoneering. You can imagine which way I’m leaning.

Chapter One: Core Concepts

Hybrid D&D uses the d20 system. This is the same system we have been using since 2000. The core mechanic of the system wasn’t greatly altered between third and fourth editions: roll 1d20, add a bunch of modifiers and compare to a Difficulty Class (DC).

I don’t have a problem with the d20 system; in fact I rather like it. The largest fundamental change that I propose is that instead of always rounding fractions down, we round them up. You see how I’m already being good to you? Actually this is an essential change if my skill system is going to work. More on that in a future post.

Fixing the Difficuly Class

The fundamental thing we need to sort out is the underlying mathematics of the game. At it’s heart the d20 system works on a very simply 50-50 rule. A 10th level fighter attacking another 10th level fighter has about a 50% chance to hit. Or to put it another way, a 10th level fighter has +10 to hit and an armour class of 20.

All the various spells, feats, talents and class abilities in any edition of D&D are designed to give your characters an edge – to allow them to nudge that 50% chance up a little – often at the expense of other statistics. The 10th level fighter might have a 50% chance to hit another 10th level fighter, but his chance to strike the lightly armoured wizard is substantially higher. Likewise the 10th level wizard might have a 50% chance to bamboozle the mind of another 10th level wizard, but his chance to lobotomise the fighter is far greater.

The problem with third edition is that it didn’t get the underlying maths right and players (often through multiclassing) could punch far above their weight in some circumstances, and found themselves counting on their foes to roll a natural 1 in others. In fourth edition a character’s attacks, skills and defences all progressed at subtlely different rates which skewed the more robust maths that drives 4e.

In the hybrid game, all the elements of the character need to be brought into line. Attacks and skill rolls need to advance at exactly the same rate. Defences need to improve at the same rate as well. There will be room for customisation within that framework – there will be plenty of scope to be above or below average, but not to the insane degree that third edition supported. You won’t find a fifth level character with +20 to their survival roll any more.

Difficulty classes in the game are divided into five levels: Very easy, Easy, Moderate, Hard and Fomidable. Obviously, some DCs are fixed. It doesn’t become more difficult to balance across a tightrope just because you’ve gone up a level. However, most DCs are relative to the character’s level. These are often opposed checks against an active or passive skill.

My intention is that these DCs will be derrived from the “average” roll for someone who has maximum ranks in a skill, starts with 18 in that skill’s governing attribute and improves that attribute at every opportunity. This is referred to as “Skill Modifier” in the list below.

You might think that derriving the “average” Skill Modifier in this fashion will set the DCs too high. After all you’re only going to have maximum ranks and a maximum stat in a small number of skills and abilities, right? Well, that is exactly my intention. A check that is Moderate should be Moderate for a trained professional, and not for a layman. Don’t forget that this Skill Modifier doesn’t take into account racial bonuses or bonuses from feats and other sources. They can make a big difference. We can discuss this at greater length in the Comments.

This “average” Skill modifier is then added to a number that represents the d20 roll. Assuming on average you roll a 10 on 1d20, the DCs would be as follows:

  • Very Easy: 0 + Skill Modifier
  • Easy: 5 + Skill Modifier
  • Moderate: 10 + Skill Modifier
  • Hard: 15 + Skill Modifier
  • Formidable: 20 + Skill Modifier

So, a fighter with +10 to hit with his sword would find a defence of 10 Very easy (95% chance to hit); a defence of 15 Easy (75% chance to hit); a defence of 20 Moderatre (50% chance to hit); a defence of 25 Hard (25% chance to hit); and a defence of 30 Formidable (5% chance to hit).

Because the maximum skill level a character can have is influenced by his attributes and his level, it is possible to work out the DCs of the five tasks for each character level. This is a remarkably strong base for building the rest of the game. PCs and NPCs shouldn’t deviate too far from this rule. It is a benchmark that weird and wacky powers can be measured against.

These maths have always existed in D&D, but it wasn’t until I really starting looking at fourth edition that I noticed them. In the Hybrid Game I am proposing a realignment of the numbers to make sure this works. It shouldn’t be revolutionary, but it will have some profound ramifications.

Fixing the Damage

The fourth edition game attempts to standardise the damage output of all the character classes. That way no one class overshadows the others. In third edition the wizard bested the other classes in his potential to deal damage at mid levels, but by the highest levels it was the fighter with his multiple attacks per round (and no chance to save for half damage) that usually managed to dish out the most pain.

I have a mind to introduce something similar to 4e’s approach into the hybrid game. No one character class should be able to wipe out all the foes in one go should they?

I propose that, on average, it should take four successful hits to drop a foe that it is the same level as you. Assuming that you only hit 50% of the time that means that combats should take eight rounds. Does that sound too artificial to everyone?

Obviously some weapons do more damage than others, some attacks or knacks or talents might be more damaging. But I think it would be helpful to look at a broader picture and say (e.g.) – could this 10th level rogue take down another 10th level character in four successful hits? If they can’t, then there is an immediate warning flag that we may have to do something to alter their damage potential.

So again, this is only guidance – but useful guidance nonetheless. And yes, it doesn’t address the problem of large or monstrous foes. We don’t want a 10th level rogue to take down a dragon on his own in eight rounds do we? But while there can be no hard and fast formulae, we still need something to start with. While it’s likely that some classes should deal less damage than others because of what they are, let’s make sure we take a conscious decision to make them that way.

Chapter Two: The World of Iourn

Briefly, I would like to talk about Iourn. Iourn was created as a generic D&D setting. A place where I could dump anything that appeared in any published sourcebook. As Iourn moves into the Hybrid system it will acquire more of a mechanical identity.

Throughout the various documents that I’ll produce for the new game, I’ll use Iourn as the default setting. I won’t include anything in the game that won’t work in Iourn, and I will deliberately tailor the rules to fit in with what has already been established in the campaign. So the whole business with the Weave and how different spellcasters interact with it, is more or less sorted.

This is a change in my old open door policy to the game. With HD&D, I will no longer feel the moral obligation to make room for every single prestige class, feat and option. I’m certainly not going to convert them all. However, all those books of all those editions are still out there. If a player makes a case for playing some variation of (e.g.) the Radiant Servant of Pelor, then we can work together at the time to include create a playable version of it.

Taking a leaf from third edition, I’ll use a selection of iconic characters to provide pertinent examples to the rules. But these characters won’t be Krusk, Tordek, Mialee, Regdar, Lidda et al; instead I’ll use Arvan, Brack, Elias, Ravenna, Raza, Nicos and whichever other PC seems appropriate at the time. That strikes me as far more fun. Elias is, after all, the poster-child for how not to jump off a cliff.


In the next installment, we move onto Chapter Three. It’s all about Making Characters.


7 thoughts on “HD&D: Core Concepts

  1. For your skill checks, your maths is slightly out ;)

    Basically, a fighter with +10 to hit with his sword would find:
    a defence of 10 Very easy (95% chance to hit);
    a defence of 15 Easy (80% chance to hit);
    a defence of 20 Moderatre (55% chance to hit);
    a defence of 25 Hard (30% chance to hit);
    and a defence of 30 Formidable (5% chance to hit).

    The “very easy” category for a skill would actaully increase to 100%, as natural 1’s are not auto failures (and in the example above, with a natural 1, he hits AC11…a hit, but for the auto-fail).

    Rolling a 10 or more (that is, AC20 with a +10) is a 55% chance of success, as there are 11 numbers (10-20) to roll, and only 9 from 1-9.

    Most of the 4E maths is based around this 45/55 chance, not a 50/50. (such as hitting and saving throws).

    This might all have a total of “absolutely no” effect :D but I just wanted to point it out, in case it did!


    As for the ‘8 round combat’, that works if you are using the 4E monster rules, and not 3E. 4E bases a monster of your level for each party member, whereas 3E worked with one monster for the party level.

    Again, for larger monsters, if you are using the 4E monster rules, this works too. A minion = 1/4 of a normal monster, so should drop with one hit. An elite = 2x normals, so should drop in eight hits. A solo = 5x normals, so should drop in 20 hits. That means that rogue needs to survive 40 rounds of soloing the dragon before hoping to beat it. Sounds fair?

    – hvg3

  2. Yes, I was rather hoping no-one would notice that.

    Obviously, the average roll from 1d20 is 10.5. It’s hard to roll a 10.5, so I to decide whether the system is based on the roll of 10, or a roll of an 11. I picked 10 because then DCs can be set in increments of 5 and it just looks neater. But you’re right, that does result in the 45/55 chance, and not the 50/50 I said.

    Does it matter? I’m not altogether sure. I wouldn’t like to say that it doesn’t matter. Maybe I should assume that a roll of 11 on 1d20 is Moderate (which makes 1 Very Easy, 6 Easy, 16 Hard and 21 Formidable). There’s no reason I can’t do that. I’ll have to think about this.

    As for the 8-round combat… yes, again you’re right. That sort of thing would only work in the 4e rules and not third edition. However, I’m certainly not beneath stealing as many good mechanics from fourth edition as I can. If my goal is to reduce the time combat takes, then the fourth edition system is a better place to start than the third.

    If it takes four successul hits to drop an NPC of the same level, and only every other strike actually connects then a combat takes eight rounds. If a dragon is five times as tough as a normal NPC of its level, then a combat against a dragon would take forty rounds. But five PCs should be ganging up on a dragon at once, in which case combat takes… eight rounds. I do love the way the maths work in fourth edition. I would be loathe to abandon them entirely.

  3. Hang on. You bamboozled me with maths.

    On a d20 there are twenty possible results. 1-10 make up 50% of the possible results, and 11-20 make up the other 50%. But I’m not interested in that. I’m interested in the mean average result. I want to know what a number is most likely to come up when you roll a d20.

    Statistically, an average roll on 1d20 is 10.5. While it’s true that a result of 11-20 will come up 50% of the time, and a result of 1-10 will come up the other 50%, a roll of 10.5 is the average result.

    My maths have to be based off 10.5.

    Now of course, you can’t roll 10.5 on 1d20 (or any other type of dice). So I have choice between setting the number at 10 or at 11. Neither is exactly right, but they are both equally wrong. So the question is, do I use 10 or do I use 11?

    An 11 will make everything just that little be harder for everyone (penalising untrained characters more than trained ones). While a 10 makes it all little easier for everyone. I lean toward the 10 because I’m inherently benevolent, and because it looks tidier. But I am willing to be swayed. What is the case for 11?

  4. I was kinda hoping it didn’t matter, but just wanted to point it out, on the chance that it did….trust an engineer to point out the clunky side of teh ideas :D

    I would personally leave it at 10, even though it makes it 45/55.

    Partially, the maths is so much easier (10, 20, etc, instead of 11, 21, etc), and partially, it favours the heroes. Yea, sure it may favour the bad guy when he’s attacking, but the heroes are going to make more attacks, roll more skill checks, and reap the benefits of that extra bit of chance that much more.

    So yeah – I wasn’t suggesting shifting it to 11, rather, making sure you realised it wasn’t a simple 50/50, in case that was ever important :)


  5. This post from Neil:

    I think you should be looking at difficulties like this: have the difficulty as average when an average member of a class is against another average member of the same class or average object (e.g. lock). i.e. an average fighter should have a, roughly, 50% chance to hit another average fighter, but crucially, a better chance to hit the average magic user and a slightly better chance to hit the average rogue. Similarly an average rogue should have a 50% or so chance to perform “stealth” type skills against the average rogue but have a better chance against the average fighter or magic user. Of course that’s not to say that you could have a particularly agile magic user or perceptive/dextrous fighter. Taking it a stage further, an average low level fighter should have a small, but definite, chance of hitting an average high level fighter. Just what constitutes low and high are up for debate…

  6. Not sure if it is too late to leave a comment on this, but I think you should know there is a bit of a flaw in your maths.

    With a 50% chance to hit and 4 hits to kill, your encounters will end with 8 rolls only 64% of the time. Here are the stats:

    Chance of getting 4 hits in number of rounds:

    4 rounds: 6%
    5 rounds: 19%
    6 rounds: 34%
    7 rounds: 50%
    8 rounds: 64%
    9 rounds: 75%
    10 rounds: 83%
    11 rounds: 89%
    12 rounds: 93%

    Hope this helps.

  7. It’s never too late to leave a comment, particularly as WordPress helpfully emails me to let me know everytime one appears on the blog!

    I never looked at the figures this closely. To be honest, I expect my maths skills wouldn’t allow it. However, the stats you’ve got there are somewhat encouraging. I don’t really want every fight to end in eight rounds, that would become a little too predictable.

    From your figures it looks to me that most fights will last 7-9 rounds. Which seems fair enough to me. Actually, it doesn’t seem fair enough. In a later post I changed my mind and decided I wanted a character to go down in three hits, and combats to last six rounds. Still, the principle still stands.

    I think as long as fights are statistically likely to end in 8 rounds (and nearly two thirds of all fights will), then it should still work. Of course, I haven’t playtested any of this yet. That will come in September assuming I can actually finish the rules by then.

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