Subterrane Surveys: Dungeon of Zenopus (per Holmes)

Today we're looking at the sample dungeon from the first-ever D&D Basic Set, edited by Eric Holmes (1979) -- what many of us now call the "Dungeon of Zenopus". This has been very influential over the years -- and just last week, our friend Zenopus Archives published a 5E conversion on DM's Guild. It may be among the best-ever starter dungeons for new players.

We'll be looking at this in two parts, because we can identify at least two versions of the dungeon that differ in significant ways. There's the actual published version, that we'll get to next time. But before we do that I want to look at the original manuscript draft by Holmes -- as shared previously by Zenopus Archives himself. See that link, Parts 47 to 54, for his notes that I'm using for the work here (compiling the statistical information together in one place).

Design: The layout differs markedly from Gygax's early fully-packed (use every space) style, as seen in his Castle Greyhawk or the Dungeon Geomorphs (upper levels). Note that initially the Dungeon Geomorphs were included in the box with this ruleset, so Holmes seems to be striking out a different (simpler?) aesthetic here. He uses a lot of empty/negative space. The halls and chambers are almost totally locked to the graph-paper grid axes (no diagonal hallways, no trapezoidal rooms; except for one circular room in S and the few rough caves in the lower-left). This new design style is perhaps similar to the sample level given in the OD&D Vol-3 text, and later dungeons like the sample in the AD&D DMG.

Many of the chambers are extremely large by basic D&D standards. Most of them are too large to see the entirety using torch light (30' distance in these and other rules), and many are too large for infravision, as well (60' distance). Room A is 120' × 100', so about one-fifth the size of Notre Dame cathedral by area, while possibly only containing beds for just 2 goblins (or a few more depending on party size). Room N is as long and likely equally wide before its north wall collapsed, containing ten sarcophagi. These rooms are far larger than anything seen in Gygax's castle Greyhawk map, shown in the Dungeon Geomorphs product, generated by the AD&D DMG random dungeons tables, etc.

Five of the 20 areas are entirely empty ("E" code on the map); or in other words, 15 of 20 have some kind of content (75%). This is a far higher rate than suggested by Gygax's OD&D Vol-3, or Monster & Treasure Assortment (which argued for just 33% or 20% occupancy rates), or shown in his Castle Greyhawk map (25% with content; see two weeks ago).

Characters: As seen before, to this point in the publication history, no explicit party-size expectations are given in either the rulebook or the adventure materials. In Holmes' draft in the wandering monster section, he keeps the same language from OD&D Vol-3 (and also the same interpretation I take from the slightly muddy language there), that on average a party of 1-3 will meet one monster, a party of 4-6 will meet two, etc. In the introduction to his sample dungeon, he writes:

Because of the nature of some of the traps in the dungeon, it is highly recommended that no one attempt it alone. If only one player is taking his or her character into the dungeon, the Dungeon Master should recommend employing one or more men-at-arms. These non-player characters can then be "rolled up" and hired out for a share of the treasure.

So Holmes seems to be saying that as few as 2 characters working together, of 1st-level each, might be able to adventure successfully here. As a new DM in the first few days after opening the D&D Basic set box, I ran several of my friends through the Dungeon of Zenopus with one PC and a single hireling (more on the results of that next time).

Monsters: There are 13 monster encounters in the 20 keyed rooms (65% occupancy rate). The encounters have a median of EHD 2, and a mean of EHD 3. This means indeed that most of the encounters should be on the order of a fair fight for just 2 1st-level PCs, in accordance with Holmes' advice in the quoted paragraph above. The total placed monster strength is 35 EHD.

In terms of wandering monsters, following his draft rules -- which are close to a copy from OD&D rules -- a party of 1-3 PCs should only be facing one 1st-level wandering monster at a time, which would be EHD 1 in almost all cases; about half-strength from the placed encounters, and should be well-manageable.  

Treasures: Eight of the 13 monster encounters have some kind of treasure present (62%). There are no treasures in rooms without monsters. It seems clear that in almost all cases, Holmes directly used the monster Treasure Type tables from OD&D, copied in his draft, because almost all of the coins treasures come in units of 1000's. (Exceptions: the pirates have 2-12 gp each individually, in accordance with the special rule for Men from OD&D Vol-2 that Holmes copied into his draft Pirates monster entry; and there is one bag of 50 gp in some garbage, possibly in line with the OD&D Vol-3 random dungeon treasure table.)

Holmes' draft has a simple rule for gem and jewelry values; 50-500 gp each. While the gems are all in this range, the jewelry is all weirdly outside this range (a belt worth 1000 gp, and rings and coronets worth 3000 gp). However, they are legitimate products if one were using the OD&D jewelry table. 

Total treasure in the dungeon adds up to about 18,000 gp. On average there are about 500 gp of treasure per monster EHD in the complex. Note that this is ten times higher than in Gygax's Castle Greyhawk, which had a ratio of only 50 gp per EHD. (!)

Magic: Among the 8 treasures, 4 include magic items (50% rate), for a total of 5 items. These include: two scrolls, a potion, a wand, and a magic sword. All but one of these are initially in the control of the wizard who is the principal of the dungeon. This is close to the same rate as seen in Gygax's own Castle Greyhawk (43%), but much more than suggested in the OD&D Vol-3 dungeon treasure table (there: only 5% per treasure on the 1st level).

Experience: Recall that in assessing Gygax's Castle Greyhawk there was a question about whether we should award XP for picking up and keeping magic items or not. That parenthetically-suggested rule in OD&D is entirely excluded from the Holmes book (even post-Gygax edit!), and so too all of the later Basic D&D line. So when assessing an adventure officially for Basic D&D, there is no ambiguity; XP comes only from monsters and monetary treasure. Also, for simplicity, we'll ignore XP from wandering monsters, since we can't tell in advance how many times the party will have such encounters (or more fundamentally, how much time they'll take in the dungeon).

Holmes' draft includes a cut-down version of the revised (reduced awards) monster XP chart fro OD&D Supplement-I, Greyhawk. See here for specifics. Using that schedule, total monster awards add up to (only) about 400 XP, with about 18,000 for treasures, for a grand total of (you guessed it) around 18,400. The monster: treasure XP ratio is about 1:45, or about 2% to 98% (probably the largest differential we'll ever see). This would be enough to promote a party of 3 fighters from 1st to halfway through the 3rd level, which seems quite generous.

On the other hand, let's consider what use of the original, simpler, XP rules from OD&D Vol-1 would buy us; assume a fixed value of 100 XP per monster EHD. The total of 35 monster EHD in the complex would gives us 3,500 monster XP, and with 18,000 in treasure, a grand total of 21,500 XP. The monster: treasure ratio would be a more reasonable 1:5 (16% to 84%), and again the total would be enough to promote 3 fighters from 1st to the upper end of 3rd level.


  1. My own design has been far more influenced by Holmes than by anyone else. This was the first sample dungeon I had access to, back in '79.

    1. Of course, this was my first book and dungeon, as well. :-)

  2. This was interesting! I've linked your work in my article about D&D modules: Dungeons & Dragons products - Role-Playing Games Resources