Wednesday, July 7, 2010

Opposed Checks House-Rule for WFRP 3rd

When I've run Warhammer Fantasy Roleplay 3rd, I've replaced the "Opposed Check Difficulty" table from the main rule book with the following chart:
If the Opposing Characteristic is:
Rated at 1 to 3 characteristics dice: add 1 challenge die
Rated at 4 to 5 characteristics dice: add 2 challenge dice
Rated at 6 or more characteristic dice: add 3 challenge dice
The various "+1 misfortune die" modifiers from the original chart remain unchanged.

Overall, it's a fairly minor change, that mostly helps the little guy. This house-rule also cleans up a few weird corner-case situations where someone with an unusually high or low defensive stat seems to circumvent the default math of the rest of the game's systems. It also removes division and comparison from the tabletop, giving standard difficulties instead of needing to recalculate difficulty by the relative traits of the participants, thus speeding up combat a little.

Note that 3 characteristics dice is human average, and 5 characteristics dice is the most a PC can start the game with. So those being the break points on Opposed Checks is reasonable and pretty easy to remember.

To explain why I made those changes, here's an example:

Let's say a character has a Strength or Agility of 3, but no Weapon Skill or Ballistic Skill to go along with it. Average and unexceptional in every way. His odds of hitting the target with a basic attack are 40% or so. I mean any target. That was assuming a Defense 1 (most armors) and 1 Active Defense. There may be freak situations that nerf his odds, but if he's attacking round after round over the long haul the hit rate stays above 35%. In general, the game has very high success rates, give him an stat just 1 point above average, or a single skill die and he'll have a better than 50% success rate.

The majority of attacks use that same math, as their difficulty is "vs Target Defense" which means in general 1 challenge die and 1 or 2 misfortune dice.

Some attacks, however, use Opposed Checks. Often these are on fairly oddball actions, or ones that don't have really big splashy effects. When I've tried to assign a compare or balance the existing actions, I keep coming back to the conclusion that someone on the design team thought that using an Opposed Check was somehow beneficial to the attacker. It's not. Instead all it does is make it harder on the attacker if their stats are unexceptional.

Let's look at that person with a 3-rated stat, who has a 40% chance of hitting any target with a basic attack. What are his odds of hitting a foe by using an Opposed Check?
  • 88% if the target's opposed trait is rated at 1.
  • 59% if the target's opposed trait is rated at 2.
  • 38% if the target's opposed trait is rated at 3 (human average).
  • 24% if the target's opposed trait is rated at 4.
  • 24% if the target's opposed trait is rated at 5.
  • 14% if the target's opposed trait is rated at 6 or higher.
That doesn't look to bad - 88% is sweet. You might think opposed check attacks are amazing at sweeping mooks out of the way. At least until you realize how rare those 1-rated traits are. Even snotlings don't have 1's. The only 1's in the game are the social traits of undead and wild animals. Outside of spells, there's only 1 attack (Backstab) that will ever face off in an opposed check vs a trait rated at 1.
An irrelevant and snarky aside: Backstab faces off against a 1 trait because it's resisted by Intelligence + Observation. There's nothing to the text of the Backstab card to suggest it's meant to be better than other opposed roll attacks. It does face some extra misfortune dice, but they come equipped with an easy way to sidestep them. I think it just got the boost (of being the only action to face Trait 1 opposed stats) by virtue of left-hand-right-hand-syndrome. One person designed the action cards and someone else designed the monster stats. I know the "design by commitee" gripe is a cheap shot on my part, but it's probably exactly what happened. As written, Backstab is best against Zombies, Boars, and huge freakin' Trolls. That just doesn't feel right to me. But, admittedly, it's a minor quibble.

That those same sorts of foes also have really low Fellowship scores is a little weird. Yes, it makes sense a Zombie shouldn't be very friendly, and shouldn't have much luck Influencing you with Social Actions. But as written there's nothing that stops a PC from using "Winning Smile" against a Zombie, or "Insulting Blow" against a Boar. Common sense and/or GM intervention is likely to prevent either, but per the RAW (Rules As Written) these mindless foes are not just valid targets, they are particularly vulnerable to social actions of this sort. I find that a bit silly.

We now return you to your regularly scheduled slightly less ranty post about math and house-rules...
If the foe outclasses you just a tiny bit, the Opposed Check rules in the main book will totally nerf you. The game assumes your odds of hitting with a normal attack will never drop below the high 30%s. Why would you pay for a special attack that might drop as low as 14%? You've dropped from hitting 1/3 of the time to hitting 1/7 of the time. Stick with your basic actions at that point.

Now let's look at the numbers using the house-rule at the top of this post. The same 3-stat individual is attacking. His odds of success under the house-rule are:
  • 59% if the target's opposed trait is rated at 1.
  • 59% if the target's opposed trait is rated at 2.
  • 59% if the target's opposed trait is rated at 3 (human average).
  • 38% if the target's opposed trait is rated at 4.
  • 38% if the target's opposed trait is rated at 5.
  • 24% if the target's opposed trait is rated at 6 or higher.
The extremes have been ironed out of the scale. There's no longer the random boost making Backstab situationally better than all other Opposed action cards. The 24% difficulty vs the hardest foes is now only a little bit worse than normal odds, and still probably worth attempting an attack. You're hitting 1/4 the time instead of 1/3 the time (or 1/7th under the normal rules). For a card like Dramatic Flourish, those 10 extra percentage points mean it might actually be worth using sometimes.

There's two other minor reasons I like this rule:
  1. The reduced variation frees up some character design space. The example above focuses on attackers with human average stats, but it's possible to have a 2-rated trait for a PC in warhammer. The odds get much worse than presented above if your stats are that low, dropping down to an 8% success rate. Applying the house rule takes some of the sting out of being below-average in a stat. Having 2 dice in something is limiting enough without Opposed Checks stomping you down further. The game system includes character classes like "Scribe" and "Rat-Catcher" so being a little substandard should be encouraged, not punished.
  2. No math, just a chart with 3 entries. The system from the rulebook required comparing stats to figure out if something was less than, but not less than half a stat. If I'm keeping track of the wounds, status, and recharge tokens per action of half a dozen goblins, two orcs, a giant boar and 3 mobs of snotling henchmen, I don't want to have to do even the tiniest bit of division in the middle of that. It was pretty minor mindless division, but it was still prone to slowing the game down or even derailing the GM's focus.

I've run the house-rule for a 6-PC one-shot and few smaller test combats, and it seems to work well, with no unexpected ripples into other rules. It's pretty tight, easy to remember, and very functional.

A few of the GMs on the WFRP forums do something similar, but they divide the opposing trait by 2 and either round down or use a misfortune die for the fraction. I don't like that because it still leaves the weird trait-1 loophole for Backstab, and because it's marginally less elegant than my system. Marginally.

An email from my friend Peter reminded me of this House-Rule, which I meant to post more than a month ago. I'd been working on some pie charts to go with it, and gotten sidetracked on other probability related topics. Thank you for jogging my memory, Peter!

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