These guys should never win!
Today I’ve been thinking about ways to remodel Warhammer Fantasy Roleplay 2 (WFRP 2) to make it more user friendly and less punishing, and in the process of thinking through the system’s underlying probabilities I have run up against a problem with the reference frame for skill tests that I think is common for many systems. The problem is a simple one that afflicts opposed skill checks: depending on who is considered to be the active initiator of the skill check, the same skill check can give different probabilities of an outcome. This situation is particularly stark in WFRP 2, though I think it might afflict other systems too. Here is a brief explanation of the problem and how it can (and can’t be) solved. I wonder if this problem is part of the reason that people get so frustrated with the WFRP 2 system and always feel like they’re failing …
The WFRP 2 opposed skill system
WFRP 2 uses a stat-based skill system to resolve skill checks. Stats range from 0 to 100 and an unopposed skill check is resolved by rolling d100 and trying to get under your stat. So e.g. if your agility is 40 then you will succeed in a basic agility check 40% of the time. There are modifications of course (skill training, etc.) but this is the basic process. For an opposed skill check, each person involved in the skill check makes their roll, the person initiating the check starting and then their target rolling under the opposing skill. For example in combat the attacker rolls for Weapon Skill and then the defender rolls their Weapon Skill or Agility in order to parry or dodge. In an opposed skill check your chance of success is always lower than your base stat: it is stat * (1 – opposing stat). This creates a punishing probability curve, incidentally: a person with a stat of 50 up against a target with a stat of 50 has only a 25% chance of success, and perversely this is the best in the game. If you have stat 90 and you are up against someone with stat 90 your chance of success is 9%. But this is only part of the reason that WFRP 2 punishes players.
How reference frame affects outcome
Consider the following example. Bob the Hapless needs to sneak into a tavern to steal one last drink, so he first needs to get past the guard at the door. He has Agility 40 and the guard has Intelligence 40, so it’s an opposed skill check, Bob’s 40 vs. the guard’s 40. Bob rolls, the guard rolls, and fortunately Bob rolls a 01 and the guard a 41, so Bob gets through. His chance of success here was 40*60=24%, not so great; this means, note, that the guard’s chance of spotting him was 76%.
Now Bob the Hapless is near the bar, but he doesn’t realize that a skaven assassin is in the room, and is sneaking up on him. So now Bob the Hapless needs to do an observation check to notice the skaven assassin if he wants to avoid being ambushed. The assassin has a stealth of 40 and Bob has an intelligence of 40, so they roll. Now Bob’s chance of success is 40*60=24%; this means that the skaven had a 76% chance of sneaking up on him.
Unsurprisingly, Bob’s chance of continually beating 24% odds is not good, and he fails the second roll – he rolls a 39 but the skaven rolls a 7. Bob is ambushed and, as one might expect, soon becomes ratfood. This is because he got rat-fucked by the system. When he had to make a stealth check with agility 40 vs. intelligence 40, he had a 25% chance of success; but when the skaven had to make a stealth check with agility 40 vs. intelligence 40, it had a 76% chance of success. For the same check!
Why this happens
In WFRP 2 there is an initiator and a defender of any opposed skill check. The initiator needs a specific chain of outcomes: her own success and her opponent’s failure. But the defender doesn’t need a specific chain of outcomes: they only need either a failure or a success. Essentially once the initiator fails the defender doesn’t need to roll, but if the initiator succeeds the defender gets a second chance to dodge the outcome. Success for the initiator is a conditional probability (on the defender failing); whereas success for the defender is a marginal probability of either the defender succeeding or the initiator failing.
This might not be a problem except that GMs tend to try to make the player the active participant in a skill challenge: if the player is stalking, then the player makes a stealth check against which the GM defends; if the player is being stalked the player makes an observation check against which the GM defends. But this desire to make the player the active participant of their own adventure massively reduces their chance of success; and until they reach a stat of about 50 this effect is punishing – and becomes punishing again after stat 50!
Does this happen in other systems?
I think this doesn’t happen in systems with dice roll vs. DC systems, because usually if the skills/stats are balanced then they cancel each other out and only the probability distribution of a single die roll matters. Shadowrun has an opposed skill check system where each player rolls a dice pool, but in this case the outcome is determined slightly differently: the defender’s roll sets a target that the initiator has to beat, effectively ensuring that if the initiator rolls well above a threshold they’re likely to win (see below for how this can affect WFRP2). I remember playing Talislanta or Aria (not sure which) and finding the same problem, that you could never hit anyone in combat, and I think it had the same underlying mechanic. I think this mechanic is used in quite a few systems, though I haven’t played them all obviously. I don’t think WFRP 3 has it because the difficulty of skill checks is set by the opponent’s attribute and this is asymmetric: in the above example everyone would have the same dice pools in all situations.
I think this problem is merely particularly noticeable in WFRP 2 because all the PCs start off so terrible that you really feel the problem.
How to fix this problem
There are a couple of simple solutions to this problem. The first and most obvious is to design a better system. A partial solution would be to require the defending character to roll under the number obtained by the initiating character and under their own skill. So in the above example, when Bob rolled 01 for his stealth check there was no way the guard could see him; but when he rolled a 39 on the second check there was a big chance that the skaven could roll under his result (which it did). This only partially fixes the problem, since if the player rolls near their stat, the number the defender needs is effectively only constrained by the upper bound of their own attribute. It also doesn’t work when one player’s attribute is much lower than another’s. I think Dark Heresy (the Warhammer 40,000 game) has a modified version of the mechanic that uses a version of this system based on degrees of success that may partly solve the problem.
The best solution is to define active and passive skills, so that for example Observation is always a defender skill and stealth always an attacker skill. This solution has two problems though: attacker skills (like hitting people and sneaking past people) will always be much, much harder than defender skills, which will encourage people to develop characters and gameplay styles based around not doing these things; but more importantly, RPGs should put players at the heart of the action so that wherever possible they initiate skills rather than defending against them. Setting up a system of skills where some are always initiated and some are always defended will mean that some players will be very good at what they do, but will never be put in the active position in doing what they do. I think this doesn’t match the ethos of gaming that most players enjoy.
Basically, skill tests should always be resolved by a single, simple dice roll that is in the hands of the player as much as possible.
Can WFRP 2 be fixed?
I just completed a follow-up session to the Slaves of Destiny adventure I did a while back, again using WFRP 3. It was a lot of fun but this time around we had a large gang of skaven slavers to fight (report to come) and it was just impossible for me to properly follow the rules – or even anything like them – when GMing all those monsters. I didn’t even have table space for the cards! I like the system but in the absence of thoroughly stripping it down and making it much simpler, it’s a good way for PCs to operate but a terrible system for the GM. I would like to be able to use the WFRP 2 rules, because all the surrounding material is great and the game has such a strong feeling, but I just hate them. However, I think with a few tweaks to the central mechanic [well, a complete change] the stat blocks, career system and everything else could be retained in their entirety, and the game become an enjoyable and frustration-free romp through a really great world. In many ways WFRP 2 is an almost perfect combination of world-setting, atmosphere, writing, art and game system: except its fundamental mechanic is broken. I think that mechanic can be fixed by dividing all attributes by 10 and employing a 2d6, Traveler-like mechanic. I will come back to this soon I hope, to describe how to do it – and maybe also test it with some of my players.
If I could find a way to enjoy playing WFRP 2 I would be a very, very happy GM …
Compromise and Conceit 
November 23, 2015 at 4:40 pm
[…] yesterday’s post I talked about my desire to redesign the Warhammer Fantasy Role-playing 2nd Edition (WFRP 2) rules […]
November 23, 2015 at 8:56 pm
You might also consider “margin of success/failure” – the amount by which they pass or fail their skill check. In your examples of Bob vs guard: Bob’s had a success and the guard had a failure, so that’s easy. To notice the assassin, Bob has a margin of success of 1, while the skaven has a margin of success of 33. 33 > 1, so the skaven wins. Let’s say that Bob had rolled 50, while the skaven rolled 60. Although they both failed, Bob only failed by 10, while the assassin failed by 20, so Bob would win.
You could also replicate this (I think the probabilities would be the same) by letting them roll under 50 + (PC skill – enemy skill).
I think this has all the features you’re looking for: it doesn’t matter who the initiator is, it keeps things at a nice even 50% when skill levels are the same, and gives an advantage to whoever has a high skill level.
November 24, 2015 at 8:53 am
I rechecked and the WFRP 2 rules do have success/failure margins, but these don’t solve the problem, just reduce its impact. Actually my proposed revised system (that I posted up yesterday) doesn’t solve the problem – it’s a fundamental problem of having an initiator and defender on a skill check, where the skills are reversible. The only solution is to set a rule that all skills are either initiator or defender (passive and active skills, you could say). I guess the problem is particularly noticable in WFRP because the effect is so punishing, and a universal complaint of the system is “I failed at everything I tried!” I think this is some fundamental binary problem with skill systems …
November 25, 2015 at 10:04 am
Properly implemented, it shouldn’t matter who the initiator and defender are. Both roll simultaneously and then compare rolls. Even if both fail, the one who fails by more is the loser – relative skill levels (and dice rolls) are the only things that count. This contrasts to what you’ve described above, where if the initiator fails, the defender doesn’t even have to roll to succeed.
November 25, 2015 at 11:59 am
This method would work provided there are not any specified thresholds for success separate to the opposing person’s skill. In WFRP 2’s original rules, both people in the skill test have to first pass a threshold before their relative successes are compared – so if the person initiating the test doesn’t make the threshold there is no further test of the defender’s skill. Thus the comparison of success levels happens conditional on the success of the initiator.
In my revised version for some reason the problem still exists. For example if both players have attribute of 4, in a stealth vs. observation check, the initiator has to roll over 8, i.e. has a 41% chance of success. This means that the defender had a 60% chance of success. But if you reverse the skill checks, the opposite outcome ensues.
Typically it works like this: PC sneaks into combat so he has to do a stealth check – which with 40% chance of success means that the enemy’s observation skill had a 60% chance of success. But then during combat an enemy enters the fray by stealth, to attack the PC. Then the PC is given an observation test to spot the sneaker, so it becomes observation vs. stealth. Then the PC has a 40% chance of success in the observation check, and the enemy a 60% chance of success in the stealth! Obviously this isn’t always a problem because often in such a situation the GM will treat the enemy as the initiator. But we don’t always do this! It depends on the flow of play, how much we want to give the PC control of the dice rolling, how many other things we’re doing, etc. And there are other skill checks that don’t have such a natural passive/active division as stealth/observation. Even if you have a consistent pattern of assignment of passive/active you’re still saying the active skill is harder: if you always do stealth vs. observation, then you’re effectively saying that for a person with stealth X and Observation X, observation is always easier than stealth. This might be true in that particular case, but is it true in all possible skill test combinations? e.g. hiding a trap vs. finding it; hitting vs. defending; casting a spell vs. resisting a spell; hiding your mutation vs. spotting it; and so on.
February 2, 2019 at 1:53 pm
Well while you’re correct about attacks and parrying, you’re simply wrong about opposed skill checks in wfrp2.
A failure by the initiator doesn’t mean the outcome is determined – you also need to wait and the defender’s roll. If the defender succeeds the opposed roll is resolved in his favour. If the defender also fails the rulebook recommends declaring it a stalemate or re-rolling.
The parrying issue can be resolved by requiring parries to succeed by more levels of success than the attack.