Conditional Injury Impressions and Tweaks

I’ve been using the Conditional Injury rules by Douglas Cole published in Pyramid #3/120 for the better part of the year now and I’m very happy how they turned out in play. Yet they are a rough diamond, and likely need some tweaks to reach their full potential. Here are some ideas inspired by my experiences.

Logarithmic Injury

A very nice property of Conditional Injury is the way robustness, wound potential and injury severity are set up, it’s a great step towards logarithmic GURPS. It works especially well in situations where there is a scale difference between combatants (for example, spaceships), you can really feel that SSRT love. The only wrinkle is the linear nature of DR subtraction in an otherwise logarithmic playing field. Without DR, we could move our rules even more in the logarithmic direction by further abstracting damage so that each attack is rated in its average wound potential, with a chance of doing enough damage to result in a potential one level higher or lower.

If we take a look at the roll probabilities of any given damage roll and how robustness thresholds and wound potentials interact, we can notice that this is what generally happens anyway. There’s about a 15-25% chance for the attack to result in a wound potential of one lever higher than its average, and the same chance for one level lower. We could convert the damage dice of an attack directly into wound potential, and handle the  chance of +/-1 level by for example just rolling 3d; a result of 7-8 or lower would indicate a wound potential one level lower, while 13-14 or higher would indicate one level higher.

But with DR, we have to make additional considerations. Looking up DR on the wound potential table and reducing the wound potential of an incoming attack by that level overstates the impact of DR (significantly in some cases, less so in others). An alternative would be to use armor as dice, another idea proposed by Douglas in Pyramid. DR would be converted to dice, those would be directly subtracted from damage dice, and if any dice remain, their average wound potential could be looked up on the table and the roll for the final wound potential made as above (or alternatively, just roll the remaining dice as damage and look up the resulting wound potential on table). A downside of this approach, if it may be called that, is that under default GURPS rules an attack can still cause injury as long as it does not strike DR of about 1.7 times its average damage. This is a departure which could be fine for some situations (firearms come to mind) but maybe not so fine for others.

… or maybe not

On the flipside, the “full” logarithmic behavior could be too coarse for application in the “couple guys swinging swords at each other” space. In a lot of games, players eke out as much ST as they can since every level increases swing damage by one, seek out fine and enchanted weapons to get that extra +1, etc. Unfortunately, anything less than +1 damage/die (which would roughly correspond to a +1 wound potential shift) is effectively ignored by Conditional Injury. To add insult to that injury, HP don’t matter outside of specific breakpoints as well. Taken together, this can be very unsatisfactory coming from default GURPS.

So if we don’t want to go on a quest for pure logarithmic GURPS, we can go in the other direction and make the mechanics more finely grained. Instead of using robustness thresholds and wound potential, we can determine injury severity based on the ratio of damage inflicted and HP of the target:

Damage inflicted in % of HPInjury Severity
10% or less-7 or less
more than 10%-6
more than 15%-5
more than 20%-4
more than 30%-3
more than 50%-2
more than 70%-1
more than 100%0
more than 150%1
more than 200%2
more than 300%3
more than 500%4
more than 700%5
more than 1000%6 or more

The benefit of this approach is that every level of HP matters, and thus every point of damage you can squeeze out has a better chance of making a difference. Injury multipliers due to damage type and hit location can either still be handled how CI proposes, or be reverted to the default GURPS behavior in which case injury severity would be looked up after any injury multipliers have been applied to damage penetrating DR.

For simplicity, every character could have a table with these breakpoints on their sheet.

Bits and Pieces

Injury Accumulation

In my experience, injuries almost never accumulate due to significant bonuses to HT in most cases. At the minimum, the bonus attained from sub-0 severity injuries should be removed. Alternatively, Douglas also has a  “save vs death” idea where he proposes using HT/2+3 instead of straight HT for some rolls, which could fit this purpose nicely.

We had a chat on this topic on the GURPS Discord, and came up with a solution I’ll try out in my campaign:

  • Instead of rolling straight HT – injury severity for wound accumulation, make a roll against HT/2+3 – injury severity (so severity -1 and lower wounds give a bonus); on a failure, your wound severity increases by 1. On success, it doesn’t, but you lose 1 FP due to blood loss, system shock etc. On a success by 5 or more, you suffer no ill effects.

This uses the same injury severity modifiers as the published version, but while they make passing the roll way too easy in that case, their interaction with the above “save vs death” roll seems much more appropriate.

Oh, I don’t really think injury accumulation should be an optional rule. I’ve already had players frustrated by not being able to cause useful injury to tough opponents due to the generousness of the accumulation rules as published, and not using them at all would only exacerbate the problem.


I’m using time-based recovery with the exception that a successful application of First Aid still reduces injury severity by a full level. In addition, I do not limit the maximum severity which can be treated with it. I have used pure time-based recovery at the start of the campaign, but that made First Aid rather useless in a cinematic game with a lot of injuries. For context, magical healing using the aforementioned time-based recovery variant is available as well albeit not as abundant as in for example Dungeon Fantasy, and there are expensive superscience medkits that reduce severity by a level (cumulative with First Aid, but only applicable once per injury).

Stuff I’m Not Using

The Pain rules seem nice but I haven’t used them yet because I didn’t want to overcomplicate the introduction of a new, already complex enough system. I don’t use the Bleeding rules because they add a post-combat effect that seems more trouble than it’s worth for my campaign, and I don’t have a need for Variable Injury. I would use Deadly Fatigue, but haven’t had a chance yet.

Variable Injury could, by the way, be a useful component of a system with low damage variance. But otherwise I think it makes the system too survivable, and it’s already more survivable than default GURPS.

3 thoughts on “Conditional Injury Impressions and Tweaks

  1. M C 2021-02-19 / 16:25

    “Wound accumulation is now rolled for any wound that’s equal to or lower in severity than your current one, not just the ones equal to it as previously.”
    But that’s wrong; injury always accumulates except for scratches.


    • chaoticgm 2021-02-19 / 17:23

      Huh, I looked over the Pyramid text again and it seems you are right. Thanks, I’ll adjust the article to reflect this.


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