Evasion & Armor

Here is a quick method for changing how armor works that has been floating around in my head. I don’t claim any originality for this system. It was inspired by Combat Musings over at The Jovial Priest and St. Innocent of Alaska over at Blood of Prokopius.

This assumes a B/X substrate. It would play well with damage by hit die rules, I think.

First, instead of AC there is an evasion score. This is 10 + dexterity mod. This is how hard it is for a character or monster to be hit. You would need to improvise the evasion score for monsters, but I think that should be easy. Sample: goblin, 12; pixie, 17; dragon, 10.

Second, armor provides a damage reduction die. Light (leather) armor is d4, medium (chain) armor is d6, and heavy (plate) armor is d8. If you are wearing armor and take physical damage, you roll your armor die and reduce damage by that much. This is similar to “soak” rules in other games, but I think this implementation integrates nicely with other traditional D&D rules. Monsters also require improv DR scores. Sample: wolf, d4; bear, d6; dragon 2d6.

That’s the core of the system. Here are a few optional rules for added detail.

  1. Armor damage. If you ever take a full damage blow (e.g., 4 points from a d4 attack or 6 points from a d6 attack), you roll damage reduction as normal, but mark down a point next to your armor. When N such points have been accumulated (e.g., 8 points for heavy armor), the armor is degraded one step (so degraded plate armor would reduce damage by d6 after one level of degradation). Armor can be repaired, probably at half cost.
  2. Weapon versus AC. Using a weapon that is “good against” a particular armor drops the damage reduction die by one step. So, plate armor would only block 1d6 damage from a military pick. Firearms could ignore armor entirely or drop the damage reduction die by one or two steps, depending on how much influence you would like gunpowder to have on your setting.
  3. Bulky armor. Armor reduces evasion by one point per class. For example, plate armor would reduce evasion by 3, leather by 1.
  4. Armor competency. The damage reduction die is limited by class hit die. So magic-users can wear plate armor, but they still only get d4 damage reduction, and all evasion and encumbrance penalties still apply. Maybe there is some method to gain proficiency with armor for classes other than fighters? That’s beyond the scope of this post, though.
I’ve worried before that this sort of system might make dexterity overly important, and I still think that is true. Another reason to use 3d6 in order to generate stats, as if we needed more.
From the armchair, this looks like a pretty slick system that would be fun to play and potentially feel more realistic to people who don’t like the “armor makes you hard to hit” paradigm.

Edit: damage reduction numbers for d6-centric OD&D using 2DTH: light (leather) 2d6 take lowest, medium (chain) 1d6, heavy (plate) 2d6 take highest. Evasion calculated using the B/X dexterity modifier, though it would not apply to anything else.

18 thoughts on “Evasion & Armor

  1. waywardwayfarer

    This is remarkably similar to something I had been tinkering with a while back. I had worked in an additional component, a coverage rating for armor according to which pieces were worn, so that an attack roll greater than Evasion + Coverage bypassed damage reduction. So, a full suit of chain mail would be the same damage reduction as a hauberk, but with less chance of being struck in a poorly protected location.

  2. FrDave

    As Roger pointed out, this has the same kind of feel that Stormbringer has (which can be a good thing). Conceptually, I like the idea a lot (I get to roll all those cool shaped dice); however, I do have two reservations.

    1) It is potentially an extra die roll every time someone makes an attack. This takes time and makes combat longer. While this might not bother a lot of folks out there, it does me.

    2) The math produces a bunch of negative numbers when figuring out the average amount of damage Joe Average Guy (JAG) would take from Joe Average 1HD Monster (JAM) per round.

    If JAG is wearing leather armor (-1 on the evasion score) and has a 10 DEX, JAM needs a 9 to hit. This means JAG will get hit 60% of the time. The average damage per round for a 1d6 attack ends up being 2.1 hp (3.5 x .6). However, JAG has an average DR of 2.5. This only gets worse with better armor.

    This suggests that combat is not only going to last longer, but over-emphasize armor and/or emphasize attacks that do massive amounts of damage. Thus, anybody that cannot either wear armor or do enough damage to get through armor is going to feel useless in combat. I have gone down this road on more than one occasion with 3.5 and Pathfinder, and it is NOT fun.

    1. Brendan

      Thanks for stopping by. Lots of good feedback.

      Regarding the JAG/JAM example, I don’t think the average damage is negative. The DR should only be factored in assuming a hit was scored, thus 60% of the time, assuming averages, JAG will take 1 point of damage (3.5 – 2.5). I agree that does seem low, so perhaps the armor dice should be stepped down? Something like d2, d3, and d4 maybe. Or d4 – 1, d6 – 1, d8 – 1. On the other hand, it does seem to be relatively realistic to me. Most of the time, if you’re trying to actively defend, your armor will take the blow. And it doesn’t prevent catastrophic blows from getting by (like d8 attack rolls 8 and DR rolls 1).

      I think the real danger would be how such a system integrated with the traditional increasing number of hit dice accumulated by PCs as they level. This might also require an adjustment to that system, though I think this would probably only be clear from play testing. And mid to high level D&D has always been a bit strange by the numbers (the example of a 10th level fighter falling 50 feet on purpose because she knows she can survive 5d6 points of damage being a traditional example, though one that I think is easily handled by situational rulings).

      I do think some level of randomness is important for the damage reduction, or you end up with problems like daggers only ever able to do 1 point of damage 25% of the time (assuming you have a flat DR of 3 with heavy armor).

      Oh, and I didn’t consider the effect of shields. Probably +1 DR.

    2. Brendan


      One other thing that I forgot to mention but intended to is that I would be much more likely to use a system like this in a setting with Firearms, like your Alaska idea, which would probably disincentivize armor use and thus cut down on potential combat grind.

  3. Hedgehobbit

    I played a ton of Stormbringer (and Runequest) back in the day and found that modeling armor as damage reduction really did force all the PCs to carry around the biggest two-handed weapons just to be effective. Runequest was worse in this regard because the damage reduction was fixed and it was fairly easy to get it up to 5 or 6 points making one handed weapons all but useless.

    I prefer a fixed all or nothing damage save as in Dragons at Dawn or the various Warhammer games (sadly not the WFRPG). This will affect all weapons equally thus allowing daggers and the like to still be usefull. By reverse engineering the combat tables of D&D, against a 1 HD monster: leather armor blocks 18% of all attacks, chainmail 35% and plate mail blocks 55%. That would be a good place to start.

    1. Brendan

      In the way I would use this, damage is by hit die (with an upgrade to two dice, take highest in the case of two-handed weapons or dual-wielding). So I don’t think it would affect weapon choice that much, though it would probably make things like flaming oil and fireballs even more valuable.

      This idea of a fixed and comprehensive damage save intrigues me, however. Following your numbers, perhaps: leather 18, chain 13, plate 10? With the same armor degradation rule suggested above, so armor would wear out.

  4. The Jovial Priest

    A really interesting take. I have yet to implement any changes to my combat system – despite my desire – mainly because I am introducing a younger generation to D&D, and while I allow myself some house rules – I want them to know they are playing D&D, not Uncle’s game.

  5. DrBargle

    Dragon Warriors has a similar model to the one you propose. Each character has a defence score, which increases with rank (level). This is a fixed amount of defence, so if you have 9 in defence you can split into three defence scores of 3 to deal with 3 attacks. It is defence that determines whether a character gets hit. Whether a character gets injured in dependent on armour, but armour does not reduce damage in the way that RQ armour does. Rather, armour has to be penetrated. Each weapon has an armour penetration dice, so bigger weapons use bigger dice. If the weapon penetrates the armour, then it does a fixed amount of damage. So, sure, plate protects you from most attacks, but when you get injured you do take damage.

  6. Peter K.

    I’ve been kicking around an idea for something like this for my own “Crude Simulation Engine” project, with a few significant differences:

    * Dodge – A character’s chance to avoid being hit is:
    10 + Dex. bonus + Combat bonus
    (Combat bonus increases with level)

    * Armor DR – No die is rolled. There is a flat DR for each armor type. Just less die rolling.

    * Armor Bypassing – Attack rolls have the following effectiveness:
    Attack roll < Dodge total, then no damage.
    Attack roll < 10 + Dodge total, then armor DR has full effect.
    Attack roll < 20 + Dodge total, then armor DR has half effect.
    Attack roll => 20 + Dodge total, then armor DR has no effect.

    Basically, determining does the attack impact the armor, or bypass it to some degree. And if it hits the armor then how much is it effected.

    1. Brendan

      Do you cap combat bonus?

      I kind of like to keep potential combat numbers relatively grounded, and model really powerful monsters like demons by requiring magic weapons to damage them, and perhaps some forms of damage reduction where appropriate (rather than just raising the AC).

      Otherwise, that looks like a very usable system. The fixed DR value per armor + ability to bypass armor with a high attack roll is a nice way to allow daggers to still damage people in plate (for example).

    2. Peter K.

      My thinking was not to cap combat bonus. High levels represent nigh-godlike attack precision and ability to avoid blows. I have no problem with low level play being the norm, but like there to be some provision for PCs or monsters to be insanely skilled if the theme warrents it.

      Monsters only being susceptible to certain attack types is still an option. And there could be “innate DR” for some monsters that can’t be bypassed without specific attack forms (e.g. “hits ethereal”) or a called shot (e.g. soft pallate only).

      Such monsters might not even have a high combat rank though. They might seem uncoordinated, but still unstoppable (like a primordial ooze of some sort).

      Another fascet is that, since the system is a bastard offshoot of 3E, size is a factor to attack/defense. Hitting the broad side of a dragon is relatively easy for a character of equal level, but you might need to find an Achilles heel to bypass it’s high innate DR.

    3. Brendan

      High levels represent nigh-godlike attack precision and ability to avoid blows. I have no problem with low level play being the norm, but like there to be some provision for PCs or monsters to be insanely skilled if the theme warrents it.

      I agree in theory (in fact, I am writing a post about this very issue right now). In practice though, I think representing “insanely skilled” is really hard to do in a way that feels satisfying.

      This is compounded by that fact that most high-skill or high-level systems probably get much less testing than low-level systems.


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