Monsters Through the Ages -- Carrion Crawler

AD&D Monster Cards Carrion Crawler
Last week on Wandering DMs we had a smashing chat with one of our favorite repeat guests, Matt Finch of Mythmere Games. As I write this, his Kickstarter for the new Swords & Wizards Complete Revised edition is entering its last few days -- you should check it out if you can. 

Matt is both epically knowledgeable about old-school D&D, and also impressively generous with his time and wisdom. After the live show he hung out for another hour to chat with he patrons on our Discord server (accessible at any tier on our Patreon). As part of that discussion, we got on the subject of Carrion Crawlers. Almost everyone involved had a different take on some part of how they should work -- and as we dug out our various books, it turns out that every one of our competing interpretations had some support from one text or another, which was entirely fascinating.

The Carrion Crawler is rather infamous for being probably the most brokenly imbalanced creature in early D&D. Positioned as a 2nd level monster on its birth in OD&D (Supplement I), it was re-evaluated as 6th level in the AD&D DMG, and got a special badge in its Monster Manual text: "... these monsters are greatly feared". Don Turnbull's MonsterMark System from the White Dwarf has an especially problematic time handling it. Frank Mentzer put forward using one as the single biggest mistake of his DM'ing career. And on and on. But what makes it the flagship for busting up a DM's best-laid plans?

OD&D Greyhawk (1976)

CARRION CRAWLERS: These scavangers will usually attack in order to insure that there will continue to be a supply of corpses to scavenge. They are worm-shaped, about 9’ in length, 3’ high at their head end, and move quickly on multiple legs. Their mouths are surrounded by eight tentacles of about 2’ length, and their touch causes paralization (save vs. or paralized). The Carrion Crawler is able to climb/move along walls or ceilings as readily as floors, thus allowing it to compete with Ochre Jellies, Black (or Gray) Puddings, and the like.

The "Attacks and Damage by Monster Type" table in this book (p. 16-19) confirms that a carrion crawler gets "8 tentacles" for its number of attacks, which is a very large number (rivaled only by octopi, squids, and hydra). The damage entry just says, "special", and the text here notes the paralyzing attack, which is really crippling (e.g., its one of the reasons ghouls punch so far above their weight class by hit dice). 

Note that no actual damage value is given -- I think this and the rust monster are the only two creatures to this point that lack a damage value or some other clear way of killing a PC (i.e., by poison or other death effect). This makes it a major trap and counterexample for any system that tries to measure monster threats by some kind of a-la-carte points system.

In our discussion last week, several opinions were put forward about what happens, as is quite likely, after a carrion crawler scores a TPP (total party paralysis). Does it just wander off, looking for actual dead meat (carrion), no-harm-no-foul? Does the DM start making wandering monster checks, who might actually kill the PCs and thus give the crawler something to scavenge (note that no duration was given to any paralysis abilities to this point). Does it presumably auto-consume the hapless PCs? Yes to all of these, depending what edition you play with.

AD&D Monster Manual (1977)




Carrion crawlers strongly resemble a cross between a giant green cutworm and a huge cephalopod. They are usually found only in subterranean areas. The carrion crawler is, as its name implies, a scavenger, but this does not preclude aggressive attacks upon living creatures, for that insures a constant supply of corpses upon which to feed or for deposit of eggs. The head of the monster is well protected, but its body is only armor class 7. A carrion crawler moves quite rapidly on its multiple legs despite its bulk, and a wall or ceiling is as easily traveled as a floor, for each of the beast's feet are equipped with sharp claws which hold it fast. The head is equipped with 8 tentacles which flail at prey; each 2' long tentacle exudes a gummy secretion which when fresh, will paralyze opponents (save versus paralyzation or it takes effect). As there are SO many tentacles with which to hit, and thus multiple chances of being paralyzed, these monsters are greatly feared.

A year later we have the 1E AD&D Monster Manual, which is almost entirely backwards-compatible with OD&D, and mostly just compiles all various stats for each monster (formerly spread around in separate pages of each book) in one place. It still gives no positive damage other than the paralysis effect, and no duration for that ability, either.

The text says that it's willing to attack living things, "for that insures a constant supply of corpses upon which to feed or for deposit of eggs". Without any specific mechanics, this could open up DM to interpret it in several ways. Maybe paralysis leads to death; maybe it waits for wandering monsters; maybe it injects eggs into PCs who get consumed by them immediately or later. The mind boggles at the hideous possibilities. 

D&D Basic Rules (Holmes, 1978)

This scavenger is worm shaped, 9' long, 3 feet high at the head and moves quickly on multiple legs. It can move equally well on the wall or ceiling as on the level. The mouth parts are surrounded by eight tentacles, two feet long, which produce paralysis on touch (i.e. when a hit is made). 

Holmes Basic is usually a faithful editorial presentation of the same rules as seen in OD&D. I briefly point out this book because it more explicitly gives a stat block for the carrion crawler that says, "Damage: 0". Zenopus Archives has a great series poring over the original Holmes manuscript for this book, which we know Gygax did an editorial pass on before publication. (And he makes the point that possibly one could argue in OD&D that by default every crawler tentacle gets a stock d6 damage on every hit, but that's taken off the table with this clarification.)

D&D Basic Rules (Moldvay, 1981)

This scavenger is worm-shaped, 9' long and 3' high with many legs. It can move equally well on a floor, wall, or ceiling like a spider. Its mouth is surrounded by 8 tentacles, each 2' long, which can paralyze on a successful hit unless a saving throw vs. Paralysis is made. Once paralyzed, a victim will be eaten (unless the carrion crawler is being attacked). The paralysis can be removed by a cure light wounds spell, but any spell so used will have no other effect. Without a spell, the paralysis will wear off in 2-8 turns.

As usual, Tom Moldvay makes the helpful decision to specify a duration for the paralysis for the first time. His stat block is back to saying, "Damage: Paralysis" (as opposed to 0 in Holmes). But most keenly he states that crawlers simply eat their paralyzed victims by fiat. (!) So DMs used to running the B/X or related systems likely have the intuition that crawlers just swallow their prey whole like a snake. No save for you.  

This same ruling is carried forward later into the Mentzer BECMI set. The Alston Rules Cyclopedia is largely the same with tiny adjustments: the stat block there says, "Damage: Paralysis or 1 point", and the text sets a timer on fast one eats paralyzed bodies: they "will eat paralyzed victims in three turns".

AD&D Monster Cards (1982)

Carrion crawlers attack with 8 tentacles that secrete a gummy fluid that will paralyze any opponents hit for 2d6 turns unless they save vs. Paralyzation. Carrion crawlers wll continue to attack as long as any opponents are unparalyzed. They will kill paralyzed creatures with their bite (DM 1-2), in order to have a constant supply of bodies to eat and to lay eggs in.

The AD&D Monster Cards are kind of a fascinating a beautiful set of products (the art at the top of this post is the front of the Carrion Crawler card). There are times I'm tempted to run a classic game by always showing players these cards, with name and info hidden on the back -- except there are too many gaps of key monsters that were never included (please, someone make a fill-in product here, take my money so I don't have to do it).

While the stat blocks are mostly identical to what's in the Monster Manual, these cards make some surprising, fundamental tweaks to certain monster rules. For example, you can see here that it specifies values for carrion crawler paralysis time (2d6 turns) and its capacity post-paralysis (a bite attack for a 1-2 damage). Other examples include specifying the duration for Ghoul paralysis for the first time in the game. So now the issue clarified for the AD&D line: a paralyzed party will clearly get TPK'd by the crawler. 

This duration and damage was copied forward verbatim into 2E AD&D, for example. In 3E the duration was given as 2d6 minutes, and the post-paralysis bite damage was raised to 1d4+1.

Big thanks to our patron Adam for pointing out this detail to us.


At the outset, carrion crawlers have a fairly open-field ability profile that DMs could potentially fill in many different ways. But over time each of the bifurcating Basic and Advanced D&D lines of the 1980s-1990s came around to specifying a relatively limited paralysis duration, and a direct way for crawlers to finish off prey that they'd paralyzed -- including some small-damage bite attack in their final forms. 

Even with that specific damage figure, their main disabling threat is of course the paralysis ability, so systems that try to mechanically crunch damage numbers will still trip up over evaluating these monsters. In the OED Monster Metrics simulator, a carrion crawler with its full 8 attacks gets assessed at EHD (equivalent hit dice) 12, while a reduced one with 4 attacks is still EHD 9. (Note that latter form is what I customarily run with, coincidentally similar to what Mentzer rationalizes in his games.)

How do you like your carrion crawlers? Are you happy with the post-Moldvay consensus that crawlers definitely terminate their paralyzed prey, or would you prefer different possibilities?


Random Walks in the Dungeons of the Slave Lords

Cover of In the Dungeons of the Slave Lords

I recently had an opportunity to run AD&D module A4, In the Dungeons of the Slave Lords, for the first time. This is of course the culminating adventure in the classic A-series Slavers tournament, famous for stripping the PCs of literally every resource and forcing them to outhink their way through a pitch-black labyrinth after being abandoned/ sacrificed to its horrors. We chatted about it a bit on Wandering DMs the other week. 

Once again, the playthrough made me realize several things about the adventure that I hadn't noticed, even having read through it multiple times since its release in 1981. (As usual, one of the pieces of dogma for this blog is: The acid test is gameplay.) One that came up in my discussion with WDM Paul is that, while the dungeon has 3 different possible exits, all the times we've run it the players have made it out through one exit in particular.

To investigate this, I took some graph-theory code I'd developed for one of my college courses, modeled the A4 dungeon as an abstract graph, and then simulated several thousand random walks starting from the entry area #1 to see the frequency that those walks run into the various exits. For this purpose, I annotated the dungeon map with extra areas 22-27 to mark otherwise unlabelled tunnel intersections (if you have your own map copy you can deduce where I put those labels, I'm sure). Then I cut out all of the mid-tunnel points that don't have any branches, places where the PCs are highly unlikely to turn back, counter to how a random walk will work (and this also simplifies the visual appearance of the graph, below). Here's the result, via the gvedit visualization tool:

Annotated & reduced abstract graph of AD&D module A4


Some observations: There are several interconnecting circuits in the section of areas #1-12 (top half of this graph), which allow numerous ways to navigate between those areas. But there's only one exit in that section, at area #10. 

In contrast to that, there's one critical bottleneck-tunnel from area #12 to #15; that's the only way to access the other branch composed of areas #15-21 (bottom half of the graph here). Despite the difficulty in getting there, that branch includes 2 of the 3 dungeon exits (at areas #19 and #21), as well as the notable Myconid colony (featured on the cover of the module, and the only place in the entire A series where negotiation can be profitable). If players never find their way to that particular tunnel out of area #12, then they'll never see any of that latter content.

So here's the results of my series of random walks -- note this is purely random at each location, including equal chances to turn around and backtrack from any location. After 10K simulations, the number of times each exit was reached are as follows:

AD&D Module A4 Random Walks 

Exit Reached Percent
10 5,360 53.60%
19 1,904 19.04%
21 2,736 27.36%

So broadly speaking, this model suggests that about half the time, players will exit from the top half of the graph, which means the exit at area #10. And the other half of the time, players will exit from the bottom half of the graph, with exits split between areas #19 and #21. Basically that toggle is a coin-flip over whether they take the tunnel from #12 to #15 or not. And consider that in this scenario, the players aren't allowed to map or properly orient themselves ("all directions should be given to them in terms of right and left", p. 3), so it's at least as likely that they'll circle back on their own path several times as they are to stumble onto the key connection. Indeed, it's the exit at #10 from which Paul & I have seen all of our playgroups escape (a small sample size, to be sure).

Regarding the difference between the two exits in the far part of our graph: our model makes it look significantly more likely that #21 is found than #19. On the other hand, it's the latter area that the Myconids are able to direct the players towards, which might shift some weight from #21 to #19; but on the other-other hand, anecdotal evidence suggests the Myconids are so frightening that it's rare for negotiations to be pursued with them. Since all of these factors are isolated in our lower branch, I don't think any such re-evaluation would affect the chance that area #10 is discovered first.

Here's he upshot: If you're preparing to run module A4, then you should prioritize being able to handle the #10 exit above the others, and more generally the whole branch that it's on, because it looks like a bit more than half the time that's how the action will play out. Secondarily you can prepare for running the more distant branch (with the complex Myconid area), in particular the area #21 exit, and not spend too much time thinking about #19, which seems to be a fairly unlikely exit point.

If you've played or run module A4, which exits did you personally see get used in play?


The Concentration Game

Man concentrating on dragon statueThe issue of "concentration" for spellcasting has come up a number of times in my OD&D games lately. For those somewhat more familiar with the current-edition of D&D, two reactions are halfway common: (a) surprise that a "concentration" mechanic existed in OD&D, and/or (b) surprise that it's so infrequently required for spells in OD&D.

At any rate: Yes, Virginia, concentration was a requirement for certain spells in the very first publication of D&D (1974). Just to reflect on it a bit more, here are all the spells which mention such a requirement:

Original D&D

  • Phantasmal Forces: "As long as the caster concentrates on the spell, the illusion will continue unless touched by some living creature, so there is no limit on duration, per se". This is the first appearance; kind of interesting it's used as means to avoid giving the spell a defined duration.

  • Wall of Fire: "The spell will create a wall of fire which lasts until the Magic-User no longer concentrates to maintain it." This is one of my least favorite uses (in that it locks the caster down to nothing but maintaining the wall while it's in use -- can't even flee while the wall serves as an obstacle). Requiring concentration while the caster directs some dynamic activity makes sense; just maintaining a static effect not so much.

  • Conjure Elemental: "The Elemental will remain until dispelled, but the Magic-User must concentrate on control or the elemental will turn upon its conjurer and attack him (see CHAINMAIL)." This is likely the most famous, idiomatic usage: concentrate on your summoned elemental or it irremediably go berserk and tries to kill you instead (which is a major downside to this spell!)

And that's it: just those 3 in the little brown books (Volume 1, Men & Magic).

A few other references can be found in Sup-III, Eldritch Wizardry, for the psionic domination ability; and in Sup-IV, Gods Demigods and Heroes, in that the Hyborean magical mirror of Lazbekri requires it (so as to function as a gem of seeing; maybe just flavor text), and that the Indian deity Rudra can cast illusions without such a requirement (as is normally the case for phantasmal forces, above).

So that's a very slight number of uses of the mechanic -- and as usual for the rules in those days, didn't really scope out exactly what the parameters of such a concentration requirement were.

The AD&D rules somewhat expand on those points, including requirements for -- gnome and halfling detection abilities, paladin detection of evil, spiritual hammer, locate animals, locate plants, wall of fire, conjure elementals, clairaudience, phantasmal forces, telekinesis, emotion, a few closely related spells, and numerous psionic abilities (in the optional Appendix I). 

One interesting point is that the 1E phantasmal force specifies that concentration ends with any movement (in addition to taking an attack, etc.), whereas the new improved phantasmal force permits half-speed movement. I find that latter rule pretty reasonable, and use it as a base assumption in my games.

Furthermore, in my Book of Spells (see sidebar) I have a tendency to include it any spells that have an ongoing detection or direction component, including (in addition to the classic ones above) -- read minds (ESP), legend lore, and move earth.

Of course, 5E D&D expanded the concentration mechanic to be a core limiting factoring in a lot more spells -- maybe something like half of all the spells in the game? When playing a caster in 5E, I routinely get tripped up by not foreseeing how many different spells have the concentration requirement, and wind up boxing myself out from good combinations and/or embarrassingly wasting a number of castings.

What's your master theory for what spells should require concentration?