X-in-6: one of my favorite tools when GMing old-school games

My kiddo and I started an OSE campaign set in Godsbarrow in November, and I’ve been making lots of little rulings on the fly during our sessions — which I love! There’s a default flowchart my brain automatically follows:

  1. Is there a rule? Cool, use it.
  2. If not, can something adjacent be adapted to it? In old-school D&D, I usually fall back on “Can this be an ability check or a saving throw?”
  3. If not, make it an X-in-6 roll.

Lots of things in Old School Essentials [affiliate link] are already X-in-6 rolls; this is a core element of the game. It’s a great, simple tool, and I love it. It’s quick, the odds are immediately evident, a +1 or -1 to the roll makes a meaningful difference, and it gets the job done with a minimum of fuss.

Lots, yes, but how many is that?

I was curious how many general situations in OSE are already covered by X-in-6 rolls, and what their breakdown of X values was like, so I made a list:

  • Listening at doors: 1-in-6 to hear stuff; 2-in-6 for dwarves, elves, halflings
  • Searching a 10’x10′ area: 1-in-6 to find something
  • Triggering a trap (if you do something relevant): 2-in-6
  • Wandering monsters: 1-in-6 per turn in the dungeon; 1 in 6 for city, clear, grasslands, settled; 2-in-6 for aerial, barren, desert, forest, hills; 3-in-6 for jungle, mountains, swamp
  • Foraging: 1-in-6, while traveling, to find food for 1d6 people
  • Hunting: 1-in-6 per day
  • Getting lost: 1-in-6 in grasslands; 2-in-6 in barren, hills, mountains, woods; 3-in-6 in desert, jungle, swamp; 2-in-6 in coastal waters; 1-in-6 in sea with a navigator (6-in-6, AKA 100%, without one)
  • Surprise: 2-in-6
  • Open doors: Varies according to STR score, from 1-in-6 to 5-in-6
  • Detect construction tricks (dwarves): 2-in-6
  • Detect traps (dwarves): 2-in-6
  • Detect secret doors (elves): 2-in-6
  • Hiding (halflings): 2-in-6
  • Using a tinder box: 2-in-6 per round
  • Boarding actions: 2-in-6 to get in position
  • Finding safe harbor in a storm when at sea: 2-in-6
  • Will a monster stop to pick up treasure you drop?: 3-in-6
  • Will a monster stop pursuing if you drop food?: 3-in-6

Handy defaults

I haven’t poked the Advanced rules yet, just the Basic ones, but even so seeing it all in a list like that makes a few things jump out at me:

  • When in doubt, the default chance should be 1-in-6.
  • If you’re pretty good at it, or it’s relatively easy, or it’s notably dangerous, it’s 2-in-6.
  • 3-in-6 is rare, and really emphasizes the situation — like just how much more dangerous the jungle is than the grasslands.
  • 4-in-6 and 5-in-6 are vanishingly rare, and never used outside of tying strength to opening doors.

This is pretty much the approach I’ve been using with Lark: 1-in-6 or 2-in-6 if it’s worth rolling at all, with a +1 or -1 depending on the circumstances, roleplaying, clever tactics, etc. I’ve absorbed enough B/X, Labyrinth Lord, and now OSE over the years that I’m sure I intuited that approach based on their rules. I’m not a genius inventing the wheel, I just like poking things to see how they work.

It’s really neat to see all these X-in-6 examples in one place, and to see how clearly the design intent comes through.

4 thoughts on “X-in-6: one of my favorite tools when GMing old-school games”

  1. I am much more a fan of “1 in X”.
    That makes it easier for me to remember what kind of roll I wanted to make when I get distracted by players chattering, and it also makes it easier for the players to recognize when “something happens”.
    I just tell them “roll a dX” and they always know that “something always happens on a 1”.

    Though it means calling for dice more often, since you can’t have anything being more probable than 1 in 4.

    1. Martin Ralya

      Okay, that’s really neat! I generally announce the chance when I roll (“On a 1 or 2, something happens”), but I like your shortcut of the chance always being 1-in-X.

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