West Marches: Two Rules Changes

02 May, 2025

I've posted on this blog about my piratey West Marches game before. In typical OSR fashion I've hacked together my own custom set of rules to suit this game, and it's ever a work in progress. Here are a couple of recently implemented rules changes.

Goodbye Usage Dice

Usage Dice is a concept I first encountered in The Black Hack (upon which I based most of my West Marches hack). The system in a nutshell:

Consumable items in your inventory (potions, arrows, marbles, etc) aren't counted discreetly, but are represented by a die (d4, d6, d8, etc.). When you use some of that item you roll that die, and if you roll a 1 or 2 you reduce the size of the die (d8 becomes d6, then d4), depleting it fully after rolling a 1 or 2 on a d4.

Usage Dice seemed super cool when I read about them but in my experience at the table they are confusing and strain the fiction a bit. Why can't I tell exactly how many arrows I have left? How can I give half of my water to my friend? What if I want to buy a smaller portion of something from a merchant? There is no clear guidance for scenarios like these.
The system could still be useful if you want to hide information from players (how many charges are left in a wand, for instance), but a single hidden die roll by the GM would likely serve equally well. Long story short: we're ditching Usage Dice for our game in favour of just tracking stuff normally.

If you want to ditch it as well, you can use this chart to determine the average number of uses you might expect from a given usage die:

• D4: 2 uses
• D6: 5 uses
• D8: 9 uses
• D10: 14 uses
• D12: 20 uses

Advantage and Disadvantage with Double Successes and Failures

My game uses a slot-based inventory system like many others. In the system you get a number of "stowed" slots determined by your stats, plus four "handy" slots which are close at hand and accessible in combat. One design goal with the handy slots was to give the GM a list of items to justifiably jeopardize when the players mess up ("ah, you flubbed your roll so the dagger in your belt goes skittering down the mountainside," etc.). However in practice there was no rule which actually triggered such a punishment, so it has never come up.
I also had an Exploits system where successful attacks would - on top of doing damage - also grant players the opportunity to attempt a non-damaging extra action, such as disarming an enemy, kicking over a brazier, throwing sand in someone's eyes, etc. This was inspired by the Mighty Deeds mechanic from Dungeon Crawl Classics. It was intended to reinforce a pulp adventure vibe but my implementation instead felt overpowered, and the frequency with which it triggered robbed it of any feeling of excitement.

To address both of these things I've come up with the following replacement:

Advantage: Roll twice and succeed if either is a success. If both succeed, gain an Exploit.

Disadvantage: Roll twice and fail if either is a failure. If both are failures, suffer an additional Consequence.

Yes, I realize this is similar to a crit hit / fumble.¹

The consequence for disadvantage should be clarified before the roll is made so the players can make an informed decision. Not so for advantage, since table time is wasted debating an exploit that may not happen, and it's all upside.

Some examples:

Advantage

• The PC is hidden from a passing giant crocodile and therefore has advantage on their attack roll. Both rolls succeed, so the players asks the GM if the crocodile could be knocked prone. The GM thinks this unlikely due to its size and broad, low stature, and suggests they could keep out of its line of sight and remain hidden. The player says they really want to slow the beast down, so perhaps they could have hurt its foot. The GM agrees, and its speed drops to 0 for its next turn.
• A character is going to make a leap across a deep and deadly chasm. They have the spring in your step trait so they gain advantage on the roll. They succeed on both rolls so they gain an exploit. The player asks if their character might find something to grip so they can lean out and help their companions over and spare them from needing to roll. The GM says they'd still need to roll, but they would all gain advantage. Everyone agrees this is fine.

Disadvantage

• The party is trying to trick a gang of bandits into thinking they're diseased so that they will keep their distance. The bandits are wise to trickery but the players are good performers so the GM grants a deception attempt with disadvantage. The GM declares that the additional consequence on a double failure is that the bandits will be incensed at the trickery attempt and become hostile. They party agrees to the deal and rolls a double failure. The bandit leaders's nostrils flare and their face turns red. "You lying sods are gonna wish you'd just turned your pockets out. Get 'em!"
• A PC is scrambling through dense forest in the dark trying to catch up to someone. The GM calls for a roll with disadvantage and says that if they fail both rolls they'll lose something from their handy slots. The player fails both rolls, so the GM rolls 1d4 which determines that they lose their musket!

Anywhoo, that's all for now. These changes are new so I can't say how they'll hold up, but they feel like they're going in the right direction.

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