Subterrane Surveys: Dungeon of Zenopus (per Gygax)

Today we're again looking at the sample dungeon in the first Basic D&D set (1979), the "Dungeon of Zenopus". Last time we looked at Eric Holmes' original unpublished draft. But after Holmes submitted that work, Gary Gygax took an editorial pass at it, changing many items on a line-by-line basis. Among his larger changes included the entire wandering monster system, the treasure tables and XP, and the monsters and treasures in the sample dungeon itself. Zenopus Archives informed us of all the details. Let's give it a comprehensive analysis.

Design: The dungeon gets a new professional-grade map, although the overall structure is largely the same. Whether the changes here also came from Gygax's direction, or were just artistic flourishes, is not entirely clear -- but the changes do seem in line with Gygaxian written philosophy at the time.

In particular, Gygax was consistent to this point that dungeons should have lots of empty rooms. The map moves in that general direction with the addition of another 3 empty rooms. This gives a total of 8 in 23 rooms that are totally-empty (35%, or 65% with some kind of content). While that's a bit lower content rate, it's still nowhere near the guidelines in Gygax's OD&D Vol-3, the Monster & Treasure Assortment, or Castle Greyhawk (respectively suggesting as low as 33%, 20%, or 25%).

Characters: We've mentioned that at this point in time neither the rulebooks nor adventure have hard specification for the standard adventuring party size. One place Gygax makes very large changes is in the wandering monster section. There, he cuts out the language that Holmes took from OD&D Vol-3 (that monsters should scale to party size at about one-third the numbers). Here he writes:
The number of wandering monsters appearing should be roughly equal to the strength of the party encountering them. First level adventurers encountering monsters typically found on the first level of a dungeon should be faced with roughly equal numbers, i.e. a party of three would encounter 2-6 orcs, 3-12 giant rats, etc. However, if the party were second level, or the first level monsters were encountered on the second level of the dungeon, the number of wandering monsters encountered should be doubled. In a like manner, the number of monsters should be tripled for third level adventures or in the third level of the dungeon if the monsters appearing are first level.
The only example he gives there is for a party size of 3. And while he addresses possibly different character levels, he says nothing about differing character numbers. So perhaps we should take parties of size 3 as the new norm? (Which seems very different from the playgroups of 12 or 20 simultaneous players we've seen in various other sources.)

You may recall from last time that Holmes has a passage in the introduction to his sample dungeon suggesting that if a player adventures solo, then they should take one or more hirelings with them (so maybe just 2 characters). This passage is left unaltered in the published version. However; we'll see below that Gygax went through and increased monster numbers and strength throughout the dungeon, so this advice is no longer appropriate.

As I said last week, when I ran this as my first-ever DM'ing (or RPG play of any sort) experience, I had my friends individually each take 1 PC and 1 hireling -- the result was that all of them died horribly on their first D&D expeditions. That formed our initial impressions of standard D&D play, and arguably, my lifelong quest to make sure that D&D adventures aren't too terribly broken in terms of balance for the expected adventuring party. 

Monsters: There are still 13 monster encounters, as in the Holmes draft. But Gygax increases monster numbers and strength throughout the dungeon. For example, he turns a 1 HD giant spider into a 6 HD monstrosity. He changes a single 1 HD giant rat into a more dangerous swarm of 2-8 half-HD rats. He increases hit dice for skeletons, a giant crab, and an octopus. He increases the number of pirates.

The median encounter is now 3 EHD, with a mean of 4 EHD (up one pip each from the Holmes draft). Also his new wandering monster tables have an average encounter strength of 4 EHD, as well, so on par with the set encounters (up from just 1 EHD in Holmes). I would suggest a party of at least 4 1st-level PCs to be on par with any of these encounters. The total set monster power in the dungeon is now 46 EHD; up from Holmes' version that had just 35 EHD (a 30% increase). 

Treasures: Gygax keeps treasure in all the same locations that Holmes does. But while in his editorial pass he notably increased the monster strength, he even more radically decreased the value of the treasures.

The primary way that he does this is that while Holmes used only silver and gold coins in both his text and dungeon, Gygax inserted the additions of copper, electrum, and platinum, and generally shifted all of the coin treasures to some lower-valued type. He also reduced the largest treasure in the dungeon, the jewelry in the necropolis room, from 3000/3000 gp to just 300/900 gp (in so doing, making them fair game for the edited jewelry rule of 300-1,800 value per piece, the lowest category from OD&D).

It should be pointed out that Gygax struck out the OD&D treasure table that Holmes had copied, and inserted a new one, which expands the Treasure Types from OD&D's A-I with added types J-T. This includes a series of per-individual monster small unit treasures, in contrast to the original types which were all in unit's of 1000's of coins. It looks particularly strange here because almost none of the new types are used by any of the monsters in this book (I think only type Q with a few gems is used in the stirge entry). This table matches the one found in the AD&D Monster Manual (1977), except that work also has space on the page for types U-Z. (See here for details.)

And another thing: In two separate places Gygax adds warning text that the Treasure Types table is only meant to be used for large groups of monsters in their lair. This recalls the rule in OD&D Vol-2 (p. 23) that treasure is only found in the "Lair", as assessed by the probability given in the Monster Reference Table (p. 3-4) -- which itself has monster numbers in the range of hundreds, and is noted as being "primarily only for out-door encounters". And that same rule is again repeated in the AD&D Monster Manual, p. 5 ("The use of treasure type to determine the treasure guarded by a creature in a dungeon is not generally recommended."). So this seems like a place where Gygax as editor seems to think Holmes essentially misunderstood the core rules (cloudy as they may have been expressed), and took action by dramatically reducing all the treasure values involved.

The total treasure available after Gygax's edits is less than 4,700 gp, a sharp drop from the Holmes version with almost 18,000 gp (leaving only about 1/4th the original treasure value). There is very close to 100 gp of treasure per monster EHD in the dungeon.

Magic: Gygax leaves all of Holmes' existing magic items unchanged; and he adds one item, a magic dagger in the hide of his now-colossal spider. This gives 5 treasures with magic out of 9 -- a 55% rate (only slightly off Holmes' original or Gygax's own Castle Greyhawk).

Experience: Gygax strikes out Holmes' abbreviated XP table, and inserts back the more detailed OD&D Supplement-I table (stopping at 5 HD to fit the available space). Using this, total placed monster XP adds up to 940, with treasures of about 4,700, for a grand total of 5,640. The monster: treasure ratio is 1:5 (16% to 83%). This reduced total is not enough to advance 4 1st-level fighters (what would balance the average set and wandering encounters) to 2nd level.

On the other hand, if we used the original Vol-1 XP method (say 100 XP per EHD) then the total 46 EHD gives 4,600 XP, almost the same as the rounded 4,700 gp treasure value; the grand total would then be about 9,300 XP. The ratio is then basically 1:1 (close to 50%:50%). And this total is enough to advance 4 1st level fighters to the 2nd level (assuming they clear out every monster and every treasure).

Possibly the low advancement under the first method highlights that the combination of Gygax reducing XP awards in Greyhawk (to about one-tenth the Vol-1 rule, at low-levels), combined with stripping out awards for magic items (in Basic D&D), has served to produce a fundamentally XP-deficient environment.

On the other hand, Zenopus Archives points out in the comments that in the Monsters section on p. 22 Gygax inserted, "As a guideline, it should take a group of players from 6 to 12 adventures before any of their characters are able to gain sufficient experience for successive levels". On the other other hand, in The Strategic Review Vol II, No. 2 (one year prior), he gave a guideline for leveling that worked out to an average of about 6 games per level. If I ballpark clearing out maybe 7 rooms per game session, then the Dungeon of Zenopus might take 3 or 4 sessions to clear, and Gygax's XP awards would be on track, expecting roughly as many sessions in another location to level-up the party.

I'll say that in my OD&D-style games for the past year or two I've been using the latter method; I plan to set monster and treasure values in about a 1:1 ratio, with monster XP and treasures both equal to 100 times the total enemy EHD, and not bothering with XP for magic items. This seems like a pretty simple, easy-to-remember rule-of-thumb, and progresses the PC levels in a reasonable fashion.


  1. Very interesting comparison. I guess the simple summary is Gygax kept things mostly as Holmes had made them at a high level (in terms of map, enemy types, treasure placements, etc.), but he increased the risks and reduced the rewards, both by rather significant degrees. I've felt like Gygax favored a very slow overall progression for PCs (whether through high attrition rates, many upkeep taxes, carefully hidden rewards, etc.) with many sudden highs and lows (you got the sword of answering! and then a jelly ate it...) from reading between the lines of his content in comparison to other modules, and this seems to support that thought. That seems reasonable considering the fairly flat power curve of OD&D PCs (fighters in particular, since I seem to recall an interview with Tim Kask where he said Gygax never really understood the appeal of other classes when players could be Conan). Gaining levels doesn't gain a whole lot aside from more hit dice (not even necessarily hit points, depending on which interpretation for calculating hit points is being used), but magic items or an influx of cash can be game-changers.

    I wonder if there would be any significant correlation between differences in the by-the-book random monster/treasure generation results and the increased emphasis on PCs gaining abilities by leveling seen in AD&D as compared to Basic's flatter approach (hewing closer to OD&D). My gut feeling is that there's probably too much noise in the random generation results to draw significant conclusions, though, and even if not, it'd probably be close to impossible to say how much was intentionally adjusting for changes in the approach of the core rules vs. multiple authors throwing stuff together and reviewers just trying to plug obvious problems before publishing.

    1. I would agree with very much of that. I think the broad arc I'm taking away is that in practice Gygax placed treasures somewhere between the very-hyper Vol-2 Treasure Table chart and the very-stingy Vol-3 Level Beneath Surface (dungeon dressing) chart.

      It's also possible that his big adjustment to monster XP, and retraction of magic item XP in Basic, weren't thought out together, and reduced advancement more than anyone expected.

      Also agree that the random encounters and treasures in OD&D vs. AD&D probably weren't comprehensively structured in a particular way. Another of my prime lessons is that the core treasure rule is DM fiat placements for the majority of it, and none of his dungeons statistically match any of the rulebook tables (and hence this series trying to dredge up what he was actually doing for designs).

  2. Almost seems like there is a disgreement about what "4 players" means.
    You have a seeming default of 3 PCs and one DM vs 4 PCs and the DM.

    1. That's an interesting take! I wouldn't have thought of that.

  3. Great analysis (both parts), it was fun to read this!

    As I mentioned recently on ODD74, Gygax also added the bit on page 22 that it would require at least 6 to 12 successful adventures to reach second level. Based on the way they played back then, I assume he means "sessions" rather than an entire dungeon, but in view of this advice (which seems very conservative to me) one would not expect the Sample Dungeon alone to be sufficient to level up a party, as it should not take 6 to 12 adventures to complete. So his revisions make sense in this context.

    The big "hidden" treasure of the Sample Dungeon is the wizard's "two giant volumes of spells" in Room S2, which should have his six spells in them (four 1st level, two 2nd). The spell books are usually overlooked as they are mentioned very briefly & without a stated value (and there is no general guidance in the rulebook on selling spell books); and the default assumption is that a MU in the party would want to save the spell books. However a clever party should be able to sell these books for XP. If the DM went by the value of scrolls (100 gp per level), they would only be worth 800 gp, but going by the value of spell research (2000 gp per level) they would be worth 16000 gp!

    1. Thanks! Good point about the sessions guideline on p. 22, I had overlooked that. We can also compare to the Strategic Review guideline the prior year (Vol. II, No. 2, p. 23), which averages out on the low end of that range, close to 6 "games" per level. (Above, I added a paragraph near the end on this.)

      Also a good point about the importance of spellbooks. Observation from my game in the last 2 years: Granted the incredibly low magic presence on the dungeon treasure table, NPC spellcaster spellbooks are the principal way that PCs get new spells in their repertoire. I really wish there was a book rule that NPC spellcasters need to have a spellbook placed (hidden) somewhere nearby. Without them, I've had PCs level-up and not have anything to fill their new spell slots with. Thus: Spellbooks are so incredibly precious that to date none of my players have floated the idea of trying to sell one.

    2. @ Delta:

      Great series. Looking forward to an analysis of B2.
      ; )

      RE Spell Books (in YOUR campaign)

      Don't you use the OD&D rules for spell-casting (in which every MU/Cleric has access to every spell in the book)? The way the original rules were written, I don't see much value to a found spell book at all, unless you allow it to be used like a collection of spell scrolls.

    3. Good question. That's definitely a piece I take from Greyhawk, that MUs only have a subset of available spells -- I think it's really interesting that we can (a) expand the spell lists, (b) introduce new spells rationally, (c) distinguish between MUs, (d) give an interesting goal to MUs to get more, etc.

      The writeup for B2 was indeed very interesting to construct (with one really irritating detail). :-)

  4. Delta:

    You appear to have a first printing of Zenopus. The copy I have lists the giant spider as HD 4+4, damage 2-8, and no save modifier (still has the AC 3 and knockdown attack).

    Does this change the EHD of this particular encounter? What would be its recommended level?


    1. You're right, my analysis was based on the first printing. My two paper copies (the ones I actually played with) are later editions... once spiders were formalized in the Monster Manual, with the top-level one at 4+4 HD.

      You kind of caught that I was cheating: the 7 EHD is for the standard 4+4 HD spider and I didn't bother to recompute that now (of course, 4+4 is about the same as 5 HD anyway). Running the simulator for the HD 6, AC 3, -1 penalty for strong poison version generates an EHD of 8 (8.46 to be precise).