Rules I Don’t Use, Replace, or Revise

I used to play a heavily house ruled GURPS variant for a long time (alternate attributes, different skill progression scheme, 3-second combat turns with completely different combat mechanics, etc), but a bunch of years ago I decided to return to the roots and get some experience in running vanilla GURPS. After some games, something clicked for me, and I didn’t see a point in all of those house rules anymore – I’ve been running GURPS with very few house rules since then. I don’t think any I use are made out of whole cloth, it’s just simplifications or slight tweaks to published rules. I don’t feel “full” house rules are needed at all, since GURPS offers so many dials you can turn to get the experience you like.

There’s a whole bunch of published rules I don’t use though – but most of them are optional anyway. It would take forever to enumerate all of them because most are just small things, so I’ll just talk about a few notable ones.

The Hit Point System

I only use hit points in pickup games and other games which are intended for a “public” audience. For what I call my “private” games, I use the Conditional Injury rules from Pyramid #3/120. Actually, I’ve used a similar system in the aforementioned heavily modified GURPS variant I used to run. But Conditional Injury is much more elegant. I use such systems because I was never a fan of a death by a thousand rat bites, and sometimes they’re more survivable and feel more “heroic” than the default HP rules, both of which are a plus in my book.

I’ve developed a way to make using Conditional Injury quicker with rapid fire attacks, and I apply one other slight tweak to it: instead of using the Robustness Threshold and Wound Potential tables as published, I just use a straight SSRT progression. Most of my house rules are like that – if possible, try to find an already existing element of GURPS and apply it.


I’ve been using Fantastic Dungeon Grappling ever since it came out, and never looked back. I even use it in my pickup games because it’s extremely simple and easy to understand. There are some situations where it takes a bit adjusting to (a couple of which I’ve outlined here), but I don’t see a reason not to use it in every game ever. Much simpler, and even cooler than the default GURPS grappling rules.

The only house rule I use was borne out of a discussion with the author – stronger characters have a bonus equal to the the ST difference on their attack rolls to break free.


Much like hit points, I only use this in my “public” games and only DF(RPG) ones at that. I vastly prefer magic as powers otherwise, taking elements from both Sorcery and Psionic Powers, though lately I’ve started experimenting with RPM a bit which I’ve otherwise avoided due to it being a completely new system and its tendency to upstage all non-practitioners.

GURPS Spaceships

While I like these rules in theory, in practice they suffer from two big problems. The first one is mostly due to my style of play – I need to flip so many switches to make the ships survivable enough and for the combat to work the way I want that I don’t feel the effort is worth it. The second problem is that the combat system is a completely new set of rules which I’ve found many players have no interest in learning.

I don’t run many games involving spaceships or other vehicles, but for when I do I’ve decided to use a modular ship construction system which is a mix of the Modular Mecha article from Pyramid #3/51 and vehicles as characters. As for the combat system – when I ran a mecha game I just treated the mecha as humans and used the default combat rules. Didn’t even bother mapping some of their stats to real world values because it wasn’t relevant. How fast can the mech run? I dunno, it has Move 6, the other mech has 5, you’re not interacting with other combatants anyway. I’ll use something similar for other vehicles if the need arises.

Oh – Conditional Injury is perfect for vehicular damage, and Mailanka has some great crippling rules on his Wiki which make it irrelevant to know which exact systems a vehicle has. He also has a great Action Vehicular Combat set of rules based on chases from Action and the Spaceships combat rules, but I don’t use those because of the same reason I don’t use the Spaceships combat system. Otherwise I would since they fit my requirements perfectly.


As written, the cover rules are very plausible and realistic. Can’t shoot a guy in a body part that isn’t exposed, and an exposed body part suffers a no greater to hit penalty than if it were targeted when its owner isn’t in cover.

Except this creates some perverse gameplay incentives that are noticeable in all but the most grounded, realistic of games. Why take cover so you can’t be hit in your torso armor, which is thicker than your face or hand armor? Why incentivize losing your arm, or skull shots by making the default, easiest target (torso) unavailable? Yes, other hit locations are harder to hit, but they offer commensurate rewards so taking anything but full cover isn’t really a win-win situation as one might expect. Especially against skilled opponents.

I haven’t done anything about this yet because the tug of plausible rules based in reality and my desire for few house rules is strong… but I might just say that any kind of partial covers gives the same penalty to hit all hit locations as it does to hit torso. Like, you don’t need to fully expose your hands and face to shoot, just partially. If your attacker suffers a -2 penalty to hit your torso, but a -4 penalty to hit your arm or a -9 penalty to hit your skull, taking cover is always a net benefit for you which is what I desire from such a defensive option. This is basically a simplification and abstraction of the existing cover rules from Basic and Tactical Shooting.

Active Defense vs Area Attacks

If you’re caught in the middle of an area attack and there is no cover nearby and your step isn’t enough to get you out of it… you’re outta luck. I mostly run cinematic games where this is completely inappropriate. So I mostly just say you can always dive for cover even when there is none… you find some microcover or whatever.

There’s another problem to this – due to the +3 to dodge while diving for cover, characters will generally always succeed at this. Yes, this makes them prone which is its own can of worms. It often turns area effect attacks into non-damaging setups for subsequent attacks. This isn’t a kind of incentive I like, but similar to cover I haven’t done anything about it yet due to my desire to keep changes to a minimum.

Honorable Mention: Unavoidable Damage on Getting Your Natural Attacks Parried

I just ignore this, it doesn’t fit the kinds of games I run. Monsters cheat. Players of characters with claws and sharp teeth like it too.

Rapid Fire in Conditional Injury

There was a discussion on the GURPS Discord between Douglas Cole, fellow discordite Dingo and myself today about simplified handling of rapid fire attacks with Conditional Injury. By using those rules as published, each penetrating hit from a rapid fire attack would need to roll for wound accumulation separately, if it weren’t more severe than the character’s current wound in the first place. This results in many accumulation rolls slowing down play so we were looking at how to speed it up. Eventually, we settled on abstracting all hits from an individual rapid fire attack into a single injury and then rolling for accumulation only once using the rules already in place. Here’s how it works.

Roll damage for all hits from a rapid fire attack normally. Note the number of hits penetrating DR, and use the highest damage one to determine initial severity. If only one penetrated, we’re done. Otherwise, look up the number of penetrating hits in the Linear Measurement column of the Size and Speed/Range table, and increase severity by a number of levels equal to the corresponding value in the Size column, plus one.

This increases wound severity of rapid fire attacks by one level for two penetrating hits, two levels for three hits, three levels for five hits and so on. Once the final severity is determined like this, it is applied as a single new wound, causing at most one roll to accumulate.

This both simplifies rapid fire attacks in a very elegant way, and makes them more dangerous on average when compared to vanilla CI.

If less lethality is desired, I’d use an alternative solution which modifies the accumulation rules instead:

Roll damage for all hits from a rapid fire attack normally. If the character is not yet injured, set their wound severity to the level indicated by the highest damaging attack that penetrates DR, and consider only the remaining ones for accumulation. If the character is already injured, look at all the penetrating hits. If the highest damaging one would indicate a more severe wound than the character’s current one, set severity to that level and consider the remaining penetrating hits for accumulation. Otherwise, consider all penetrating hits for accumulation.

Now check for accumulation (if any penetrating hits remain). Out of all the hits considered for accumulation, figure out the base penalty to the accumulation roll due to wound severity based on the highest damaging one. Make an accumulation roll with that penalty, plus a penalty equal to the number of hits considered for accumulation. If you fail, increase wound severity by one level as normal.

This variant results in less severe wounds from rapid fire attacks than the first one, which may be preferred in games where rapid fire shouldn’t be significantly more dangerous than a hit with a vibroaxe, for example.

On the flipside, it’s not nearly as elegant which is why we originally discarded it in our discussion. It modifies wound accumulation rules instead of “core” CI rules. This isn’t ideal because the accumulation rules are already the least solid part of CI and something that could be thrown out entirely without loss if a better solution could be found.

Reflections on Conditional Injury Tweaks

In my previous post I’ve suggested some tweaks to Conditional Injury and now that I’ve had some time trying them out, I thought I’d share my impressions.

More Finely Grained Severity Thresholds

I’m using the variant where the default GURPS injury multipliers due to damage type and hit location are applied before looking up severity. My players were happy that there is now more differentiation between their characters, and were motivated to increase their HP scores more than previously.

However, after a while we forgot about this because we’re using an injury calculator, same as we did for the default Conditional Injury rules, so for us the benefit isn’t very noticeable. And statistically, it doesn’t really matter because the way Conditional Injury handles it by default produces the same results on average as this approach. So I can only recommend this if your group likes the additional detail and is really bothered by the original system being that coarse grained, or if they find the default GURPS injury multipliers noticeably easier to use than the Conditional Injury ones.

Injury Accumulation

The decision to use HT/2+3 instead of straight HT has proven to be a great one, as the frequency of accumulation actually happening now feels just right. On the other hand, losing FP if you don’t pass the accumulation roll by 5 or more is very easy to forget and experience has shown that it is a nice detail, but not crucial. I’ll definitively try to remember it more often because I like making FP matter.

A side benefit of this is that cyclic damage works better (assuming you just let it inflict normal CI wounds, without tracking it separately). It’s still not great, but it’s much better than with straight HT rolls for accumulation and it’s quite workable, especially if you pay attention to losing FP unless you pass by 5 or more.


Since my last post I’ve started using the pain rules from Conditional Injury instead of shock, and I can’t see myself going back ever again. I like them that much! They add a very nice effect of injuries lesser than reeling mattering more than just in that instance when you take them, incentivising the players to take care of them instead of just ignoring severity -2 and lesser ones.

But with all of the usual HT rolls made due to injuries and the extra roll for accumulation, adding another roll on top on that can be a bit too much. Which is why I do the following:

  1. roll for accumulation if already injured
  2. make a death roll if warranted
  3. make a roll to stay conscious if warranted
  4. make a single roll for knockdown/stunning and to determine the effects of pain

The roll to avoid knockdown/stunning gets +3 from High Pain Threshold which also makes sense for the roll to reduce the pain level, so they might as well be unified. The only bump in the road here are injuries to vitals and skull which apply a penalty to knockdown/stunning since that penalty should not affect the pain roll, but it’s easy enough to take that penalty into account for the knockdown/stunning part but not for the pain part. As a bennie to my players, if a knockdown/stunning roll isn’t indicated, I consider the pain roll to have been automatically successful as well. This effectively adds just one extra roll when compared to vanilla GURPS instead of two and I’ve found it a significant improvement in my games.

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.