Monsters and Treasures in the B/X Dungeon

Getting to work on some dungeons for my next campaign, I want to stick as close as possible practical to what the Basic and Expert rules actually advise as guidelines to see how that really plays out in actual play. I have found that most of the moving pieces in this game are set up very deliberately to form a larger system, and not everything does what you first expect them to do coming from later games. I have learned that it’s almost always best to first pinpoint what you don’t like about the results of a mechanic before you start modifying the mechanic. It’s hard to improve something when you don’t know how it actually performs as designed, and you can easily miss out on something cool if you replace it before having it properly tested. So straight up B/X with only the TSR attack roll procedure replaced it will be for the start of the campaign.

The GM guidelines for making a dungeon in the Basic Rules recommend about 1/3 of rooms to have creatures, 1/2 of which possess treasure; 1/6 of rooms to have a trap, 1/3 of which are guarding a treasure; 1/6 of rooms with a special feature like magical effects or weird machines; and 1/3 of rooms being empty, 1/6 of which have a hidden treasure. For simplicity, lets assume here reaction rolls are made with no Charisma modifier, so half of all creatures encountered will be hostile. In practice, it’s can be considerably less.

In an 18 room dungeon, these fractions come out as nice even numbers, and it’s also a good scale for a mid-sized dungeon or level of a larger dungeon. This gives us the following lineup of rooms.

  • 3x monster with treasure
  • 3x monster
  • 1x trap with treasure
  • 2x trap
  • 3x special
  • 1x hidden treasure
  • 5x empty

Assuming the party spends 1 turn in each of the 18 rooms and 6 turns exploring and mapping the corridors, we get a total of 24 turns. After every 5 turns, the party needs to rest for one turn, which is 4 additional turns for a total of 28. There is a 1 in 6 chance for a wandering monster every 2 turns (or just 1 in 12 every turn), so we can expect 2 random encounters over those 28 turns. With the six monster rooms, that’s a total of 8 monster encounters, and rolling their reaction gives us an average of 4 fights.

(Those 4 fights cause additional wandering monster checks, which at a 1 in 6 chance produce an average of 2/3 encounters, or a 1/6 chance for another hostile creature. Small enough to ignore here.)

I think thia is quite an interesting tally for an 18 room dungeon: We can expect about 30 turns spend in the dungeon, with 4 fights, 4 nonhostile encounters, 3 traps, 3 special features, and 5 treasures. This is much less than I expected. And I love it! With a distribution of content like this, I can see how a place can feel like an old abandoned ruin. Very different from the fortified outposts that make up most dungeons I am familiar with.

Something that had never occured to me before is that 2 out of 5 treasures located in a dungeon will be in the possession of creatures that mean the party no harm. That puts the players into an interesting position. They probably won’t try to rob a group of nonhostile elves who are exploring the dungeon themselves, but what about a pair of ogers who can’t be bothered to try beating up the PCs? Players might still want to steal from them, and perhaps even kill them to prevent future attacks on travelers on the nearby road. Very interesting stuff.

The Basic Rules also recommend that about 1/4 of XP players gain in a dungeon should come from monsters, the rest from treasures. You could use the treasure tables to generate treasure hoards, but that’s something I always found too bothersome, as a dungeon full of simple insect monsters would have completely different amounts of treasures than a dungeon that is a big bandit lair. My prefered method is to tally up the XP values of all the room creatures and multiply that by 3 to get the amount of gp for all the treasure in the dungeon. (Nothing for wandering monsters, because those are supposed to be undesireable to enconter.) Then I just put the coins in the treasure hoards on the dungeon map as seems appropriate, with the arbitrarily chosen magic item added here and there. (I actually put another amount of treasure equal to the XP of the room creatures into hidden secret rooms that I don’t expect the players to find most of the time, as an additional challenge.)

Interesting stuff. I can’t wait to see how this will play out in practice.

4 thoughts on “Monsters and Treasures in the B/X Dungeon”

  1. Typo: You say “1/4 of XP players gain in a dungeon should come from treasures” but you mean 3/4 from treasures.

    Interesting analysis, though; you’re right about that distribution feeling more like exploration and less like a commando raid.

    1. You are correct. I checked all the numbers several times to not make a stupid mistake, except that one.

  2. “The GM guidelines for making a dungeon in the Basic Rules recommend about 1/3 of rooms to have creatures, 1/2 of which possess treasure; 1/6 of rooms to have a trap, 1/3 of which are guarding a treasure; 1/6 of rooms with a special feature like magical effects or weird machines; and 1/3 of rooms being empty, 1/6 of which have a hidden treasure. For simplicity, lets assume here reaction rolls are made with no Charisma modifier, so half of all creatures encountered will be hostile. In practice, it’s can be considerably less.”

    AD&D 1E has roughly similar numbers.

    1. Followed these proportions for a quick dungeon written with my spouse, and it seemed like a really helpful framework.

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