HD&D Update: Armour Class

Quite a while ago now, we looked at Hit Points and Damage. During that discussion, I talked about armour class in HD&D and how I wanted armour to reduce damage, not make you harder to hit. We had a chat about the various problems inherent in such a system, but didn’t actually make any head way in coming up with answers. As I turn my attention towards equipment and combat, it’s time to take another look at this – and to finally hammer out a solution.


In third (and fourth) edition, the DC to hit an opponent in combat is their armour class. Wearing armour gives you a higher armour class, and therefore makes you harder to hit. In HD&D this role has been replaced by your Reflex Defence. The role of armour has no bearing on how easy it is to hit an opponent. Therefore, in HD&D, armour has to mean something else. Logically, it should stop you from taking as much damage. I don’t think any of us will dispute that.

As a quick aside, none of what follows has any bearing on shields. Shields are used to deflect attacks. Unlike armour, shields are designed to make you harder to hit: they don’t absorb physical damage, they redirect it. Shields will add a bonus to your Reflex Defence in HD&D.

Originally, I thought that armour could provide a character with the HD&D equivalent of damage reduction (or “HD&D AC” as I refer to it in the rest of this article). The damage taken by the character is reduced by a certain amount. That works, but there are issues if a character’s armour is so tough that nothing can get through it. It’s fine for awesome monsters – PCs tend to find a way around these things – but if the 5th level fighter in the plate mail cannot be bruised by any of his opponents then damage reduction becomes game breaking. I think we’ve started to see this with Brack in the League of Light  campaign. His DR 8/adamantine is an incredible advantage.

Having looked in various different places for inspiration, the answer (or at least some potential answers) were right under my nose. The third edition Unearthed Arcana supplement suggests many variant rules, including two for treating armour very differently. Both of these are reprinted on the d20 SRD site under Armour as Damage Reduction and Damage Conversion. Pop over and read the original text, and then come back and I’ll examine both of these ideas separately below.

Armour as Damage Reduction

This is my original idea given the third edition stamp of approval. Notice that the text from Unearthed Arcana doesn’t do away with the concept of armour making you easier to hit. Basically, the rules divide the armour bonus of every suit of armour in two. One half remains a bonus to AC, the other becomes damage reduction. In HD&D we can’t afford to have armour giving you any bonus to your Reflex Defence, so we are largely just looking at the rules for turning the D&D concept of armour class into Damage Reduction (HD&D AC).

I think it’s interesting that Unearthed Arcana doesn’t just port the entire armour value over into a DR system. Chain mail make give +5 to your AC in the normal rules, but it only grants characters a DR of 2/–. The lesson we can take from this is that DR values need to be kept low. I can get behind that. The question is where we set the level of damage reduction. My proposal (for all the armours in the third edition PHB) are as follows. Remember that “HD&D AC” is the same as damage reduction:

Armour 3rd Ed AC HD&D AC
Padded +1 1
Leather +2 1
Studded Leather +3 1
Chain Shirt +4 2
Hide +3 2
Scale mail +4 3
Chain mail +5 3
Breastplate +5 3
Splint mail +6 4
Banded mail +6 4
Half-plate +7 4
Full-plate +8 5

The immediate problem is that reducing the third edition AC down to the HD&D version pushes the values of all the armours closer together. Chain mail, scale mail and breastplate are all identical in the amount of damage that they can stop. Of course, there are other ways to differentiate between armours other than just stopping power. Things such as the armour check penalty, the cost and the maximum Dex bonus all need to be taken into account. Certain types of weapons (piercing, bludgeoning or slashing) will be more effective against some armours than others.

Natural Armour and Damage Reduction

But it isn’t just artificial armour that we have to worry about. Monsters with thick hides have large natural armour bonuses to their AC in third edition. Equally, some creatures have Damage Reduction on top of their armour class. How do we handle that?

The formula form Unearthed Arcana is as follows: Divide the natural armour value by 5 and round down. That becomes the DR value against all physical attacks. For example, a great wyrm red dragon has a +39 natural armour bonus. That gives the dragon DR 7/– in this new system. Now a great wyrm red already has DR 20/magic. But in third edition damage reductions that are different, do not stack. So the dragon would have DR 20 against all attacks, unless the foe was using in magic weapon in which case it would have DR 7.

However, in HD&D, damage reduction (or armour class as we’ll call it) always stacks. It makes sense. Often the third edition DR value is meant to represent a thick hide. So, here’s my proposal for HD&D: Divide all the DR values in the Monster Manual by two. Divide the natural armour by five. Add the two together and round to the nearest whole number. Does that work? Let’s take a few examples and find out:

Great Wyrm Red Dragon: DR 20 (20÷2 =10), Natural Armour 39 (39÷5 =7.8).
HD&D Armour Class is 18 (10+7.8, rounded up)

Brack Ogrebane: DR 8 (8÷2 = 4), Natural Armour 3 (3÷5 = 0.6).
HD&D Armour Class is 5 (4 + 0.6, rounded up)

Iron Golem: DR 15 (15÷2 = 7.5), Natural Armour 22 (22÷5 = 4.4)
HD&D Armour Class is 12 (7.5 + 4.4, rounded up)

Fire Giant: DR 0, Natrual Armour 8 (8÷5 = 1.6)
HD&D Armour Class is 2 (1.6 rounded up)

Pit Fiend: DR 15 (15÷2 = 7.5), Natural Armour 23 (23÷5 = 4.6)
HD&D Armour Class is 12 (7.5 + 4.6, rounded down)

Well, that seems to work. And don’t forget that worn armour stacks with the above. So Brack in Plate Armour would have an HD&D AC of 10. Fair enough? Shall we pursue this system?

By-passing HD&D AC (aka Damage Reduction)

Just to remind you all, that the HD&D AC should not be seen as an impervious barrier to damage. Yes, every attack that strikes you has the value subtracted from the damage done. But there are a number of ways to get through the protection offered by the armour, or thick skin. Here are some examples:

  • A critical hit automatically by-passes HD&D AC.
  • Every successful attack does a minimum of 1 point of damage under HD&D rules.
  • Certain weapons give attackers an advantage against certain armours. For example, piercing and stabbing weapons are more likely to go through chain mail than bludgeoning weapons.

Damage Conversion

Or shall we take the other suggestion from the Unearthed Arcana, which I have to say is really quite interesting. Now, these rules depend on us using a system for subdual/nonlethal damage that is similar to third edition. I have no problem with that, the system works as well as anything I’ve seen. If you don’t know what the system for nonlethal damage is in third edition, you can pop over to the d20 SRD and find out. It’s okay, I’ll wait.

In this system, there’s no messy conversion for armour. The armour bonus of the suit of armour becomes the amount of damage that the armour converts to nonlethal damage with each hit. In this system, characters wearing armour don’t last any longer in combat than unarmoured opponents. But they are much less likely to die, and find that they recover from their wounds much more quickly than their unarmoured friends.

However, a degree of double entry book-keeping is required. When you’re damaged you need to make a note of nonlethal damage separately. Ideally, you would make a note of real damage counting down from hit point total, and a note of nonlethal damage counting up from zero. When the amount of nonlethal damage you have taken exceeds your current hit points you fall unconscious.

The rules in Unearthed Arcana suggest that characters in armour ignore all nonlethal damage (such as kicks and punches) up to ther value of their armour. I’m not entirely sure that this needs to be the case, but I’m willing to be guided on the matter. It also mentions that this system creates issues with Regeneration; but that assumes regeneration in HD&D will work the same as it did in third edition – and I don’t think that it will.

Natural Armour and Damage Conversion

But how do we handle natural armour? If a great wyrm red dragon converts the first 39 points of damage from any attack into nonlethal damage, then slaying a dragon just got much, much more difficult. But then, shouldn’t it be? Is there really a problem with most physical attacks just bouncing off the dragon and eventually dazing it into submission? Critical hits and energy attacks (no argument here, we’ve all see the poll results) bypass the protection of physical armour anyway. I don’t think that, even if we adopted Damage Conversion, we would have to trim a monsters defences.

A Damage Conversion system in HD&D would not sit will next to a separate system of Damage Reduction. If we adopt Damage Conversion then the whole DR mechanic will have to go out of the window.

I would probably rule that a character’s third edition damage reduction value can substiute for natural armour in the Damage Conversion system. So the great wyrm red dragon has DR 20 and Natrural Armour 39, so it uses the higher value of 39. Brack Ogrebane has DR 8 and Natural Armour 3, so he’d use the higher value of 8. The first eight points of damage from any attack against a butt-naked Brack is converted into nonlethal damage.

Pros and Cons of Damage Conversion

In this system, the chances are that any armoured enemy or monster than you defeat isn’t actually dead. Whether this is a pro or con depends on the circumstances. It does mean that if a PC goes into battle wearing armour, the chances are that he is going to survive. That’s certainly something of a boon for PCs, and works well with the way that I run my game. However, the mechanics are also slightly unbelievable because someone in full plate is just as likely to go down in combat as someone dressed only in a thong. That said, it does reflect the fact that even armoured characters are battered when they are hit in combat.

In terms of mechanics, I prefer Damage Conversion to Damage Reduction for the HD&D game. It means that PCs can have high armour values, but armour alone isn’t going to keep them up and moving in combat. It means that heavily armoured characters won’t prolong combat. Remember that shorter combats is a big goal of HD&D. Damage Conversion would go a long way to helping me achieve that.

Additionally, the Damage Conversion system is not so bogged down with maths. I don’t have to try and balance armour values and average damage and hit points, because it wouldn’t really matter. We can also allow the damage conversion gained from natural armour to stack with the damage conversion gained from armour. So that red dragon in plate armour is going to convert the first 47 points of damage from all attacks into nonlethal damage. That’s not going to stop the party defeating the dragon after all.

So what do you think? There will be a poll on this, but I’d like a discussion first. Damage Reduction vs Damage Conversion: you decide!


12 thoughts on “HD&D Update: Armour Class

  1. Damage conversion is a very interesting idea for a third edition game but I don’t see how it fits with HD&D. The Unearthed Arcana rules state that armour converts the AC value into non-lethal damage in addition to giving a bonus to Armour Class, not instead of. Armoured characters are just as hard to hit as they always were. If you ignore this part of the system and just take the subdual damage element, I really don’t think armour is good enough. It’s not slightly unbelievable that someone in full plate is just as likely to go down in combat as someone dressed only in a thong. It’s completely unbelievable. I really can’t see it working if AC doesn’t make you harder to hit as well.

    I’m not overly keen on the other system either (sorry) but it is the preferable alternative if you want to use reflex as the main defence against attacks. I really don’t like the narrow differences between types of armour. Studded leather and leather give the same protection? What’s the point of having both then? Armour check penalties and the like, would just make you take the lighter armour very time. I feel the differences should be greater. After all, if you’re not expecting people to have chainmail until level 10 then why not have it give five points of damage reduction. If full plate’s not available until level 18 then give it a DR of 8. Would that unbalance things too much?

    • Are armour types linked to level? Surely any rich noble can afford full plate mail regardless of their level. Whoever you’re facing in battle will have the equipment best suited to themselves: professional soldiers will have better armour than conscripts, nobles will have the shiniest, best armour available to them. Having armour doesn’t necessarily make you proficient, I admit. Would that influence what benefit you get from it or not?

      Personally, the Damage Conversion rules seem a little silly in game terms, though I understand Neil’s preference for them.

      I was quite drawn to the idea of a small pool of hit points below 0 – a `death throws` segment which may prolong life a little. Characters hitting this section make a save and those failing pass out. Those passing remain conscious but unable to act – picture the screaming wounded on the battlefield. PCs could have a bonus to fighting through it or decide whether they want to stay down or not when thy hit this pool. Obviously those fighting through would be most likely to die whereas those who collapse accept they are beaten and may live on. It could still run alongside the bleeding to death rules we currently employ.

      Damage Reduction feels better somehow. Perhaps the death throws section could counter the possibility of messy death every time. The pool could vary depending on creature or level as you want but once you enter it you’re out of combat and condsidered defeated – unless the PC or special monster has the ability to fight on. It could be the equivalent of a `Bloodied` condition, though at a more critical stage in combat.

      Shoot me down if you disagree. I think this has potential to keep characters alive unless they’re too stubborn or stupid to give in (we’ve all played this way at least once) at which point you genuinely risk character death.

  2. I prefer the damage reduction system myself, though like Daniel I feel the reduction values of the armours will need to be increased in some cases. I like the idea of non-lethal damage eventually overcoming a heavily armoured opponent, a fighter in platemail could eventually be bludgeoned to unconsciousness even if no attacks pierced his armour. So i would suggest that if say your platemail gave a DR of 8 and you did not recieve enough damage to overcome this you should still receive non-lethal damage equivalent to your opponents strenght modifyer. This way burly fighters would indeed slowly (but not that slowly) bludgeon one another unconscious, but a weedy wizard with a dagger would have no guaranteed damage to a well protected knight. Also this way you would likey render your opponent unconscious through a combination of lethal and non-lethal damage. This would enable players to lose fights without necessarily having to die, unless of course the monster was always intending to eat you in which case being just KOed is just as bad!

  3. I think an earlier blog suggested that the availability of heavier armours would be limited for PCs. Lower level PCs shouldn’t be able to afford the best equipment.

    I quite like James’ idea of incorporating a low level of subdual damage into the main damage reduction system. I don’t think we should over-emphasise the idea of subdual damage though. I have absolutely no problem with most combats being potentially lethal. It makes combat much more exciting if you are at serious risk of death.

  4. This is what happens when I’m away from the computer for a day. Everyone starts posting things to the blog at once!

    I will grant that my affection for damage conversion may have something to do with how much easier it will make the job of game design. I would take exception to Daniel’s comment that armour in this system isn’t good enough. Even without providing a bonus to AC, any character wearing armour is likely to survive a fight. That’s a big advantage in anyone’s book.

    However, I can sense a movement against Damage Conversion even in these few comments, so let’s put it to one side for the moment. I’ll dust it down if someone out there sees fit to rally to its cause. Anyone?

    To take by Daniel and James’s points: I have no problem with increasing the AC values of armour. Even putting them back to the level they are in third edition is still on the table. That would put plate armour back to AC 8. In truth, that’s what I always intended to do. But…

    The problem I then have is with natural armour. Many of you eloquently convinced me that the most realistic course was to have natural armour stack with worn armour. But what happens if a character with high natural armour puts on a suit of armour? They would be untouchable!

    A longsword does 1d8 damage. If we’re being generous and saying the sword is in the hands of soldier with 18 Strength, the weapon does 1d8+4 damage. That’s a range of 5-12 damage, with an average of 8.5.

    If plate armour has AC 8, it ignores the first 8 points of damage. That means that longswords are unlikely to go through it at all. What happens then if we have a Dragonborn in plate armour (AC 10), or – god forbid – Brack Ogrebane in plate armour (AC 16). Is that not game breaking?

    It also means that two-weapon fighters (who have many attacks that do a relatively small amount of damage each) are at a disadvantage against armoured opponents, then two-handed specialists. This isn’t necessarily a bad thing, it’s just an observation.

    As I mentioned above, you can bypass all AC with a critical hit, all attacks do a minimum of 1 point of damage regardless of the AC, and so weapons might defeat or diminish the protection of certain armours. But is this enough to balance the potentially enormous armour that some PCs can acquire?

    Really: tell me. If you think it’ll be okay, then I’m happy to playtest the game that way. But if you don’t think it’s okay, I should I be looking for other checks and balances for armour. What are those limitations?

    Finally, James: I like your subdual-damage idea in principle. I’m cautious about implementing it as it fundamentally changes combat. It may work better as a special talent available to certain fighters rather than a blanket rule that applies to everyone.

  5. Malcolm, you get your own reply!

    In the post Daniel refers to, I think I said it was likely that heavier armours probably wouldn’t be available to low level PCs. This wouldn’t be because of a nebulous and arbitrary rule, rather that low level PCs probably wouldn’t have the opportunity or the funds to acquire expensive armour (especially plate). That was certianly the case in second edition, where paladins always had to wander around in plate mail because they couldn’t afford anything better.

    I did toy with the idea of building this in the rules, and assuming that (effectively) DR increases as you gain levels. However, I think I’ve pretty much rejected that idea, as PCs always tend to find a way to get around things. It didn’t seem appropriate to count on it.

    On your other point: I haven’t decided on what mechanics I’m going to use for wounded and dying characters – although the Combat section is not too far down my list at this stage. I will definitely work your ideas into one of the options I present for discussion. Being able to make a superhuman effort and fight on when you know you’re dying is happily in keeping with the ethos behind any D&D-type game, and should be encouraged.

    Of course, the question is how we actually do it. Fourth edition let’s a character make death saving throws if their hit point total is between zero and half their maximum hit points expressed as a negative numer (so a character with 100 hit points could go down as far as -50). Of course, 4e characters can’t actually do anything while they are making saving throws.

    In third edition some specific classes (like the Frenzied Berserker) can act normally when in negative hit points. There’s a lot to consider here, but I think it’s a good idea on the whole. Of course, it’ll make it very hard to knock down villains, and may encourage cutting your foes into tiny pieces just in case they’re tempted to do something heroic.

    But I’d love to use the term “Bloodied” for this. That’s inspired.

  6. Neil says:

    Damage reduction is better than damage conversion in my opinion, though I like James’ idea. However you don’t seem to have taken into account the fact that currently HP increases with level and that has forced you to increase damage commensurately. Armour therefore means less and less as you increase in level (as I mentioned in a previous blog I believe). Your reply was that you would have armour increase with level,I was sceptical at this and now it seems you are dumping the idea. So, what are you going to do to make sure armour doesn’t become an irrelevance at higher levels?

  7. Economics and social factors will prevent low level characters from getting their hands on very expensive armour – and it’s the expensive armour that offers the most protection.

    As they increase in level certain fighter-types can choose talents and feats that improve the benefit they get from wearing certain types of armour. Equally, higher level spellcasters will gain access to spells that allow them to augment or replace mundane armour with magical effects.

    The problem with damage reduction of any sort is that it doesn’t scale well with levels. It’s always going to be more useful at low levels than higher levels. If there was a way for characters to proportionately increase their DR as they gained levels, then I would probably reject it. It would make HD&D feel too much like a game.

    Armour grants a certain amount of physical protection. That’s just how it is. Armour worn by a high level fighter might offer more protection to the fighter if he is specialised in its use, in the same way that a sword in the fighters hands does more damage. But it’s not going to scale.

    While, armour will never become an irrelevance, (DR 8 is always nice to have), it will become less useful at higher levels. What am I going to do to address this? Probably nothing. I’m not sure that it really matters to be honest.

  8. Neil says:

    8 DR may be nice to have but it becomes a statistical irrelevance (at best) at high levels and at worse a liability (negatively modifying skills for example). Your suggestion of increasing armour with talents may work however…

    The problem of course is that you are insisting on escalating HP and damage with increasing level. IMHO levels should increase skills and talents, nothing else. I know your argument is that it wouldn’t be D&D but then I have never liked D&D!

  9. I think I have a solution for your problem here. No really, it’s something to think about.

    HD&D Combat: You have (roughly) a 50% chance of hitting a foe the same level as you. Each attack does one third of a character’s average hit points. Therefore a combat between two opponents of the same level should take six rounds.

    The “each attack does on third of a character’s average hit points” actually means that your character should be able to inflict that much damage in one round. Not necessarily in one attack.

    Say, for sake of argument, an average 10th level character has 60 hit points. That means that an equally average 10th level character should be able to inflict 20 points of damage each round. Your 10th level wizard attacks once with a fireball that does 20 points of damage. Your 10th level fighter attacks twice with his sword. Each hit does 10 points of damage.

    The difference? Well, magic bypasses armour anyway. Let’s not open that can of worms again. But, the damage reduction from armour applies against every attack. Someone with AC 5 who is attacked by the fighter from the above example actually only takes 10 damage (5 from each attack).

    This is how Damage Reduction scales with level. Remember that armour only applies against physical attacks. Those characters making physical attacks increase their damage as they go up in levels largely by dint of making extra attacks each round. Armour defends equally against all attacks, so it scales with level regardless of what level you are.

  10. Might i also suggest feats or talents that improve armour DR, such as armour specification (that already exists). If armour specification and improved armour specification both increased an armour’s DR by 2 then by taking both a fighter could potentially have DR 12 in plate perhaps. Level requirements could be along the lines of 8th and 16th respectively for the feats.

  11. James: Yes. I think that martial characters should have just as many feats and talents available for defence as they do for offence. Such characters will be able to make better use of their armour, and wield this shields with greater panache.

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