Rescaling Wilderness Encounters

Went to design some D&D encounters, and once again got thinking about the balance of monsters in the wilderness. Recall the top of the monster table in OD&D Vol-2:

Here we see what we now call the "humanoids" (at the time, "giant-types"), and there's a vast difference in the numbers appearing between the 1-HD types and the types larger than that. Previously we looked at summary statistics for the OD&D wilderness encounter tables, and saw enormous variation; most specifically in the danger between those army-types versus the non-army types. Let's take another perspective: here's a frequency table of the average total EHDs (Equivalent Hit Dice) for every separate encounter listed in the OD&D wilderness encounter tables. 

Notice that the x-axis is roughly logarithmic, and that the results are bimodal: there's a big clump of encounters in the 20-50 EHD range, and a separate clump in the 200-500 range. Statistically this kind of bimodal distribution is often taken as a hint that something weird is going on, that you've mixed up two distinctly different populations in your data. In this case it's simply the difference between the army-types and the non-army-types in numbers. For monsters with maximum numbers of 100+, the average encounter EHD is about 200; for those maximum numbers below 100, the average encounter EHD is only about 40.

How might we resolve this? Personally, I'm not entirely sure who was ever in favor of these giant armies in wilderness encounters in the first place. Even Arneson in the First Fantasy Campaign complained about them, and looked for interpretations to reduce their numbers. Here are some proposed options:

  • Arneson in FFC has a system which asserts the full numbers appearing are for in-lair encounters only, and squads actually roaming in the wilderness outside be only 10-60% the lair numbers. On average that reduces numbers to about 1/3 listed.
  • If we compare the average total EHDs above (40 for small-numbers, 200 for large-numbers), then we could roughly balance them together by reducing the army-types to about 1/5 the numbers listed for wandering wilderness encounters.
  • If we look at the Moldvay-Cook B/X rules, we see what they did is reduce the numbers for humanoid types to about 1/7 the OD&D numbers. (Varying between 1/3 and 1/13 for the various types.) This is shown in the table below.

Hmmm, which solution to use? In particular with the Arneson FFC system, I've tossed this for a long time, and I've made myself something of a pariah in some circle for finding it simply infeasible on its face (his suggested system there is to actually pre-populate every hex of the campaign map with multiple encounters and play out interactions between them every campaign year). Aside from that, solely from the numbers we're looking at, two drawbacks I can identify: (a) I really, really don't want to have to make an additional roll and percent multiplication on top of all the other variegated rolls for every damned encounter (or even a simplified roll-and-divide-by-3 for every encounter), and (b) it reduces all wilderness types by a like amount, so the bimodal challenge for the numerous humanoids is not resolved. (Although in its favor, maybe there's some charm in only encountering a single dragon, chimera, gorgon, etc., in the wilderness, with batches reserved for lairs.) So that pivots us to look favorably, once again, at edits in the direction of the Moldvay-Cook rules.

A highly notable observation: The 1-HD types that appear in bulk-size in OD&D are precisely the types against which Fighting-Men get attacks as per their level (e.g., 10th level fighter gets 10 attacks per round against goblins)*. They are precisely the types against which magic such as charm person and hold person are effective. Many days now I think that it's this multiple-attack rule, present in OD&D/AD&D but missing from B/X, which marks the single biggest enormous mechanical difference between the two systems. It's possible that the wilderness army sizes in OD&D are scaled specifically to assume high-level fighters destroying 10 enemies every round of combat. I haven't specifically done the simulations needed to develop alternate EHDs under the fighter-many-attacks rule, but it's possible that alone would collapse the bimodal encounter curve down to a single well-balanced population. If we don't play with that as a universal, then we instead deserve a fairly radical reduction in humanoid numbers, as we see in B/X. 

You may be able to detect that a lot of this thought process springboards and echoes our two recent discussions on the Wandering DMs about the Action Economy and how many things one can do in a single round (with fighter-many-attacks being the biggest difference between editions). 


* Excepting Gnolls, but they too were 1-HD in the pre-publication draft of D&D, and then 2-HD afterward, so it's likely that their retention of army-sized numbers was an editing oversight.


  1. One thing that everyone misses in Moldvay/Cook is that the listed number encountered in lair is for dungeon lairs; as noted in the number appearing entry on p. B30, monster lairs encountered in wilderness will usually be 5 times the number normally met in dungeons.

    1. That's a really great point, and I did overlook that myself (it's really buried!) when preparing this post. And it's restated on X27, too.

      Of course, my goal in this post was to focus on actual-wandering monsters outside the lair. Maybe this is helpful to turn around and say that Moldvay guides us in interpreting the big OD&D numbers appearing as for full in-lairs only, with about 1/5 likely in wandering bands -- much like Arneson, and exactly in line with the stats I produced here. Once again big points for Moldvay.

      Thanks a bunch for that reminder!

  2. In some ways the marauding armies are even more troublesome... A medieval population has ~90% involved in agricultural work, so an army of 150 men under arms should have 1500 peasants somewhere backing them up. This is basically a barony.

    On the other hand, the Hundred Year's War featured a number of ex-mercenary companies that had basically gone brigand and were reaving the country side. I see these Army sized units as largely reflecting this historical threat.


    At low levels the way to deal with these companies should be evasion, silver-tongued role play (aided by a good reaction roll), or bribery. Low level characters that charge into combat with an entire Free Company on the march deserve what they get.

    At higher levels they should be scattered by forcing morale checks, ideally. If hewing to the Chainmail rules, the mere appearance of a Superhero or Wizard on the field should force a reaction roll. Killing the leader, a sizeable percentage of the force, or displaying overwhelming/terrifying capabilities (high level magic?) should also force morale checks.

    At higher levels these are also good encounters to play out with wargame rules. A typical warband is perhaps 15 figures worth of units.

    1. That's not bad, although for the Chaotic nonhuman bands it seems to present more of a problem to those low-level parties (presuming parley/bribery isn't an option per the "Monsters will automatically attack and/or pursue" rule in OD&D). So you'd be always evading and hoping for success every time or it's always a TPK.

    2. Luckily the outdoor evasion rules heavily favor small parties. :)

      Party of 4-9 vs. an "average" band (26-60% of typical numbers) evades 50% of the time.

      If the party has greater speed evasion odds increase by 25% (i.e. 75%).

      If the party wins surprise (which they should 1/5 of the time) then evasion chances are doubled (which I'd rule as "roll twice").

      If evasion fails then there's a 50% the party is caught only if the monsters are faster ("pursuit" on pp 20 of U&WA). If the party is faster or speeds are equal it seem the only consequence is to be moved a hex in a random direction, be forced to spend some time resting, and soak up another random encounter roll.

      So really the only way a decently mounted small-ish party will be cornered is by being surprised in the wilderness.

    3. @Chris I think that's a very interesting point. As usual for D&D the organization hides the most salient point: if the adventuring party is faster than the monsters they can choose to avoid the encounter unless they're surprised. The entire rest of the rules boil down to an overly-complicated series of saving throws if the monsters are faster.

      The implication of that is that it's really, really important for an adventuring party to make sure they're faster than the monsters, or at least faster than the armies of monsters.

    4. There's this weird clause in there about "a die is rolled to determine if pursuit will continue", but (a) there's no definition of what counts as success or failure on that roll, and (b) that's actually the only way to end the pursuit situation outside of melee. AS written there's essentially an infinite loop in there (and same problem exists in AD&D as I recall).

    5. Again, this may be me being dense, but I've assumed that the Evasion roll is the die roll being talked about. Pursuit ends when evasion is successful.

      Hmm... I suppose that means you could read it as even if there's no chance the monsters catch the party (party is faster), each iteration moves the party 1 hex in a random direction... and then once the pursuit ends they have to spend the next i/2 days resting. I'm not sure what I think about that.

    6. Yeah, I've seen multiple people claim they resolve it that way. And also that they fold in the Chainmail fatigue rule so the primary end-result of encounters is that the PCs are fatigued for a follow-up encounter.

      The re-use of the "evasion" chance was likewise my first instinct at one point, but I'm a bit weirded out the term "die" when the percent chance would require "dice" to be thrown. Now I think it's quite possible that the reference was the "will pursue on a roll of a 1-3", for castle inhabitants, at the bottom of the prior page (p. 19). Problem is, that again leaves monsters as always-pursuing and hence an infinite loop in the pursuit process.

    7. I think any reading that results in an infinite loop can be disregarded. Now, maybe the castle rule could be re-used but this time applying to all pursuers, but they pursue until you succeed in evading seems conceptually pretty sound. And maybe it's interesting as far as game-play if that forces you into a hex some ways distant from where you had the encounter.

  3. @Delta I've always read the "Monsters will automatically attack and/or pursue" rule in OD&D as specifically pertaining to *underground* encounters. Granted the location of a rule is very weak evidence in OD&D, but it just didn't occur to me to also apply that outdoors. And now that I'm actually thinking about it, I like the reaction chart too much to use "always attack/pursue"; I'm more inclined to go the other way and apply the reaction chart even in the dungeon. Along the lines of "the monsters know what they're doing" straight up attack is not always the best option, and certainly not always the most interesting.

    1. I can see a desire for a different form of play. That said: Even the wilderness evasion rules have a similar clause, "Pursuit will take place whenever... a party is unable to evade monsters".

    2. So that leaves me wondering when the Reaction Roll table ever comes into play. Only when the monsters are intelligent and the players are an obviously superior force?

    3. That's definitely my reading as the default dungeon-crawling rule.

      Of course, we probably all agree that DM fiat applies, so if there's a particular monster who set up as open to negotiation, then that takes precedence.

      There's also the similar reaction table on Vol-1, p. 12, that notes monsters may be lured into service with an offer from a like-alignment PC.

      In practice, I usually go for some kind of reaction roll if the PCs specifically call out in a known language, hold off on hostilities, and make some kind of parley (often with a hefty penalty for general monstrosity). But if they don't have a chance to initiate that, then the default monster mode is to be aggressive.

    4. I definitely agree as to the default dungeon crawling rule; if I were to employ reaction rolls in the dungeon I'd definitely regard that as a house rule. Maybe overland encounters are also supposed to default to aggression, but...that leads to the problem you've noted of the outrageous EHD of army encounters. Maybe having them be open to parley, with a Neutral reaction tending towards demanding a toll or service like castle inhabitants, is a reasonable alternative to scaling them down.

      One thing I notice on re-reading the castle section is that while you roll to see if the occupants are hostile, that just seems to be to determine the alignment of the inhabitants. The *actions* the inhabitants take (joust, tithe, geas, or toll) don't seem to depend on their hostility or alignment.

    5. That's a good observation with the castle inhabitants. Maybe if there were a hypothetical Lawful Lord, they'd tend to skip that and just give hospitality?

    6. It paints an interesting picture of the world if even Chaotic Lords joust honorably with Fighting Men and will host and provision the party if they lose. I'm always torn between running Rules-As-Written on this kind of thing, just because it is so odd, or saying no, of course you have to adapt this to the feel of the setting as you've imagined it, to make it *your* world.

  4. I don't really think there was any kind of game design intent in mind when gygax wrote these numbers. I'm inclined to believe he just thought how these creature tend to behave when wandering in the wilderness. Or how many of them usually appear in his chainmail combats. Things like that. That's why: "Referee’s option: Increase or decrease according to party concerned (used primarily only for outdoor encounters)."

    But I don't think it's an "option". Unless, like you said, fighters can attack multiple times. Never tried though to see if it really works.