Megadungeon mechanics part four: a universal table of wandering monsters

I started writing this a few months back, in response to some interesting posts on wandering monsters from Lich Van Wrinkle and noisms. As so often, I failed to finish the post off - but I'm now incorporating its substance into my series on the megadungeon.

In their respective posts, Lich describes mixed results in his first experience of using wandering monsters 'properly' while noisms takes against them somewhat, especially in the dungeon:

In the artificial and enclosed 'dungeon' environment, though, I've always thought that something stinks about random encounters. Unless the encounter is with a being that already exists within the dungeon key, and is assumed to be moving around (that is, if the encounter is with a being that is extraneous to what is already plotted), then one is forced to simply put out of one's mind the question of where it came from. Why is this giant slug, which the random encounter table just threw up, suddenly here? Where was it before? And why is it that it it does not appear to have had a material effect on its dungeon surroundings prior to this point? 

Like Lich, I didn't use wandering monsters much or at all in my first incarnation as a GM. In part, that was because I started out with RuneQuest, which lacked the concept of the procedural dungeon crawl. And in part, it was because my adventures tended to be sketchy affairs in which a complete map was a bonus and there was never enough prep time for extras such as wandering-monster tables. 

That's not to say that I didn't use dynamic encounters - but they tended to be of the "some guards come round the corner" variety when things started to lag. 

I've still got plenty of time for that approach. But since I've been using Basic D&D for the nine months and running of our daily lockdown campaign, I've used wandering monsters a lot, and I like them. So, I think, do the players. Wandering monsters formed the basis of whole sessions on the Isle of Dread; as noisms notes, "the wilderness is all random encounters". 

A good table of fauna offers lots of instant adventure, especially when two or more rolls are used together. One highlight in our campaign involved the PCs glimpsing a roc on the wing from atop the Isle of Dread's volcano; when they descended onto the plateau and encountered a mastodon, I had the big bird swoop down and snatch it - much to the players' horror and delight.

But what about the dungeon? Wandering monsters are the quintessence of the dungeon crawl, I think, because they communicate to the players that dungeon-crawling is a dangerous business and that they should be quick, quiet and careful. And they also bring the setting to life. 

So where do these monsters come from? Noisms argues that the "only reasonable answer as to where randomly encountered monsters in the dungeon come from is: outside, or from further down". I don't think that's quite right - or at least, I think that these and other answers are easy to rationalise even in an "naturalistic" dungeon.

Now, I agree that wandering monsters should fit the environment. Each dungeon - and probably each dungeon level - should have its own tailored table. But I'm thinking about universally applicable categories that can be intuitively filled in for a given area of the megadungeon. Let's consider eight of these.

Patrols

This is the easiest and most obvious sort: patrols of humanoids (or similar) that live in the dungeon. You can divide these into 'home' and 'hostile'. So, if a dungeon level has mutually antagonistic orcs and gnolls in it, a home roll in orc territory brings orcs while a hostile roll brings gnolls - and vice versa. How do the hostiles get there? Most likely by following the PCs, hoping to exploit the carnage that they've created - and perhaps to pick off the depleted adventurers. Rationalising their route should be easy, presuming that the PCs have come through no-man's land to get to the orc section. The gnolls have simply followed in their (bloody) footsteps.

Stalkers

While patrols probably want to prey on weakened foes and parties alike, other creatures might be specifically interested in the party. They might be predatory, or they might be looking for security, company or even friendship. So, this category can include scavengers hungry for fresh corpses, beings that want protection in the dungeon (and what better escort than a bloody-handed bunch of murder-hobos?) or those interested in something the party has: past owners of treasure, perhaps, or their minions. If Moria is the ur-dungeon, then Gollum is the ur-stalker. 

Vermin (a.k.a dwellers in the wainscotting or the Wolves in the Walls)

One obvious way to have dungeon vermin suddenly appear is simply to have them come out of the walls. I've often used kobolds in this way: their tunnels riddle the dungeon but are too small for (most) adventurers to get down - and too dangerous even if they could. Yes, your halfling might squeeze into a kobold crawlspace, but the excursion probably wouldn't end well. 

This gives a nice rationale for why weak creatures like kobolds survive and even thrive in the underworld. Rather than inhabiting large and easily invaded caverns, they live in twisting tunnels; their communal spaces are almost impossible to access. And it also explains why they can crop up at almost any time or place in the dungeon. They tunnel and burrow constantly, the entrances to their crawlways are cunningly concealed, and they're always creating new ones. 

Kobolds are just one example of creatures in this class, of course. Giant rats, giant beetles and many other smallish, burrowing beasts fit here nicely, as do stirges that roost in the recesses of the dungeon but fly through its corridors when on the hunt. 

Squeezers (through cracks)

Monstrous oozes and jellies are pretty much a D&D invention (drawing on shoggoths and the Blob, of course), and they provide another easily explainable source of monsters. Where did that thing come from? It dripped through the ceiling. Oozes gonna ooze.

Raiders

Now, these are typically from the outside (or above or below). I'd differentiate these from patrols, above, in that they're not on regular duty or simply being opportunistic, but have mounted an attack against the area of the dungeon in which they're encountered. So, while these could be the orcs/gnolls from across no-man's land on the same level, they'd appear in far greater numbers than a patrol. But they could be hobgoblins from a nearby stronghold or bugbears from the surrounding hills. They might signal their attack with drums or horns, and the party might initially just encounter their scouts or vanguard - giving the PCs the opportunity to make something of the situation. Repeated rolls in a single session would typically indicate encounters with different elements of the raiding party. Raiders could also be other adventurers, of course.

Rampagers

Another dangerous category, this: big monsters on the hunt, whether from nearby caverns or from deep within the earth. This might include trolls, landsharks and umber hulks. If these creatures exist on the dungeon level, their coming will prompt other inhabitants to bar their doors and retreat to their fastnesses. And it could be signalled by howls, heavy footsteps or trembling in the earth.

Haunters

Given that most dungeons have witnessed many scenes of slaughter, you'd expect a few ghosts to be clanking their chains. Different bestiaries assign specific roles to synonyms for ghost, but we can usefully divide this class into apparitions: harmless but disturbing visions that merely show something that happened in the past - from a march of doomed troops to a murder; unquiet spirits: ghosts that want the party to do something for them - bury their bones, avenge their death or return some object to their grave; and evil spirits: hostile ethereal undead of the D&D spectre or wraith sort.

Apparitions are perhaps the most interesting class. In a science-fantasy setting, they might be fragmented holograms (as in Serenity or Prometheus). In any setting, they can be used to hint at some tragedy from the past. Perhaps the PCs see grim-faced warriors in bronze armour march down the corridor - and then encounter animated skeletons wearing that same armour elsewhere. And perhaps these apparitions aren't visible to everyone. You can have the whole party make a save vs spells; if everyone passes, they'll still be spooked.

Personalities

An easy way to bring the dungeon to life is to ensure that its most celebrated inhabitants don't simply sit in their room waiting for adventurers to arrive. There are two obvious categories here - the 'home' encounter, which might be the orc chief visiting his lieutenants or interrogating prisoners; and the rarer 'hostile' encounter, in which an eminence from another part of the dungeon has arrived. A 'hostile' result could actually be a welcomed guest - what matters is that it's someone or something who's not on their home turf. Previous random encounters might give clues to this. If you've had a 'hostile' raiders encounter previously, a subsequent personality might be the hobgoblin commander striding in like Darth Vader in the Hoth base. If you haven't, he might be here with his bodyguards to plot mischief in alliance with the orc chief. 

So, those eight categories might give us a table like this:

D8                    Category                        Encounter (D4)

1                        Patrols                           1-2. Home (2d3)   3. Hostile (2d4)   4. Outsiders (2d6)

2                        Stalkers                         1-2. Ghouls    3. Protection-seekers 4. Treasure-seekers

3                        Vermin                          1-2. Kobolds (2d6)  3. Giant rats (2d6)   4. Stirges (2d8)

4                        Squeezers                      1. Gelatinous cube (1)  2-3 Black pudding (1-2) 4 Grey ooze (1-3)

5                        Raiders                          1 Home (4d6)  2. Hostile (4d6)  3. Outsiders (4d6) 4. NPCs (2d4)

6                        Rampagers                    1. Umber hulk  2. Trolls (d3) 3. Landshark 4. Purple worm

7                        Haunters                        1-2. Apparitions 3. Unquiet spirits 4. Evil spirits

8.                       Personalities                   1-3. Home        4. Hostile

Over a session or two, rolls on this table should illustrate the dungeon's history, politics and ecology. 

And while they should challenge the players, they should also provide them with opportunities. A hostile patrol offers the prospect of a temporary alliance. A treasure-seeker might obtain its goal in return for local knowledge. If a 'home raid' takes 4d6 of the bugbear warriors out of the complex, PCs who have snuffed their torches and concealed their pack animals may have the chance to fall upon a lightly defended bugbear lair. If the hobgoblin chief is talking to the orcs, then he and his bodyguards won't be at home if the PCs come knocking.