Caves of Chaos for Pathfinder 2e

One of the challenges of being a GM for a West Marches style of campaign is coming up with content where it’s easy for a large number of players to interact with the plot, while keeping the challenge rating flexible. My husband recommended Keep on the Borderlands, a classic module published in 1979 and written by none other than Gary Gygax.

I bought it from DriveThruRPG, and I’m glad I did. Not only is it an interesting piece of gaming history, but it’s an excellent adventure, even today. Converting it to work in 2e took way less energy than I was expecting, even though the module is old enough to have grown children of its own.

What is it?

Keep on the Borderlands has two halves to it: A keep that the players liberate and then mold, and the Caves of Chaos, which serve as the main threat. The Caves of Chaos aren’t quite as dramatic as they sound. It’s basically one huge map that features a number of caves, some interconnecting, some not. I ended up not using the “Keep” part of the module (the group already has a functional town), but the Caves of Chaos were well worth the price of the module.

And yes, I recommend grabbing the module. Not only is it a short, interesting read, but it has some tips on how the denizens caves should react to a bunch of adventurers running around and causing trouble for them.

Why use it?

Some of the advantages of using the Caves of Chaos:

1. Solid maps. The layout of all of the caves are great. There’s plenty of room for a group of PCs to move around, but they have enough corners and doors to make line of sight important.
2. Great dynamics. While you could, in theory, just use a key you find online for the Caves, I recommend giving the module a read. It recommends actions for various NPCs, and suggests how the caves might change over time as more of them are cleared out.
3. Diversity of creatures. It’s not just goblins! The caves feature all sorts of enemies, giving players varied challenges that still make sense.
4. Easy to scale. This might be more PF2 than anything else, but I found the caves to be fairly easy to scale to different levels. This is super important in a West Marches campaign, where you never know what the APL is going to be (though I did cap it at APL 3)
5. Lots of pretty resources. This module has been out for a while, so the amount of player-created content is high. I found no shortages of maps, keys, and guides. I even found maps that were redrawn to work with Roll20!

What I had to change

Keep on the Borderlands was absolutely written for wargamers. The number of expected mobs was huge, and the playing field was much larger. The squares were ten feet, and it wasn’t unusual to have a room filled 10 to 15 mobs. I ended up switching to five-foot squares, and drastically reduced the number of enemies.

There were also a few creatures I had to change, since they’re either too high level, or they don’t exist yet in Pathfinder 2e (as of this writing, only two of the Bestiaries are out). For example, the medusa was straight out, and stirges haven’t made it over to PF2 yet. I ended up swapping in new creatures, since I didn’t feel like writing my own, and it isn’t like there’s a shortage of options to choose from.

The original maps work off of 10′ squares, which I changed to 5′ squares. It wasn’t like we needed the room, after all, since I wasn’t throwing dozens of goblins at the players.

Getting converted

For each of the maps, I decided that I would keep the general theme, but set up at least three types of encounters: Trivial, Moderate, and Severe, with one Extreme tossed in one of the caves for fun. Because I didn’t know what APL I would be working with, I went ahead and created scaled versions of each encounter. That way, I didn’t have to worry running out of lower level caves, nor did I have to worry about a group of level threes tearing through a bunch of goblins.

Then, I made a table of rough conversions from the module to PF2. This way, I could go back to it as I built out the caves. Most of the creatures were a straight conversion, though it was nice to know what level range I was working with. If a family didn’t go high enough, I’d grab something from another family, or I’d toss a challenge adjustment on one of them. The only creature I had to toss out completely was the medusa, but a hag worked well as a replacement, hidden among the prisoners.

Once that was done, I set up the encounters for each cave. I did this for three APLs (one through three), because one of the downsides of a West Marches campaign is that you never know who is going to show up. It was a little more work, but in the end, it was worth it, since it greatly reduced the amount of time it took me to set up a cave.

Setting up the maps

Remember how I said player-created content was a huge benefit to running this AP? I had no shortage of wonderful, detailed, re-imagined maps. I ended up going with the cheekily named “Caverns of Entropy” from Roll20 user Keith Reinig. Even better, right after I bought the set, he added another one with dynamic lighting.

I also grabbed the overland and player maps from Weem as a reference for players between sessions. As they explored, I added their notes and the cave layouts, which cut down on players accidentally keeping vital information to themselves (something none of the players would have done intentionally).

Finally, I added a page in Roll20 for all of my prepped creatures. I ended up using this holding pen so much that I think I’ll keep this around even after I’m done with the caves.

Running the caves!

Now that everything was set up, I was ready to let players make a wreck of my plans. I decided to play it relatively straightforward: The valley appeared near town due to some magical shenanigans and a non-combatant NPC was tasked with getting adventurers to clear it out. This gave the players a hub to work around, since it was presumed that all information was shared with him, and he shared said information with each group. Each session started with players gathering at his shop, where they were shown a map and told details that the previous adventurers had uncovered. From there, they’d decide what they wanted to do, and then set out.

I allowed players to scout one cave entrance per excursion, with a particularly good roll allowing them to also get details about neighboring caves. I’d give a hint as to the kind of creatures inside based on the trash outside the cave (or lack of it). Intelligent creatures might have broken weapons outside their cave, while unintelligent creatures might just have piles of bones. Enemies with military discipline might have neater piles, while a more chaotic group will have stuff strewn everywhere.

After any scouting, they’d tell me which cave they’d decided on, and I’d put them on mute for ten minutes while I set up. Because this is a mixed level server, I never knew what the APL would be, but having the creatures and encounters set up beforehand saved a ton of time. Once I came back, they’d clear out whichever cave they’d chosen, with a soft-limit of 2.5 hours. Once time was up and they were out of combat, they had to leave, even if there were still creatures roaming around. Since I often run during the week, I can only stay up so late.

Once the players returned to town, I’d update the map with what was cleared and any notes that were made and post it to the Discord, as well as a synopsis of who went and what the players found.

How’d it go?

Prepping and converting the Caves of Chaos was no joke, but it was so worth it. I’d guess that I spent around 10 hours converting and scaling encounters, setting up maps, and creating tokens, but this lead to twelve sessions where I had to do minimal prep. To be honest, if I hadn’t obsessed about scaling and instead just scaled everything to APL 2, I could have shaved quite a bit of time off of that prep.

Also, the maps? I wasn’t kidding when I said that they’re truly awesome. Modern map-making tends to focus on a beautiful backdrop to what is essentially an open playing field. The CoC caves have hallways and rooms and dead-ends and secret doors, leading to a more dynamic playing field as activity happens outside the line of sight, PCs get separated, or they get penned in between two different groupings. The maps are also interconnected, which allowed players to sneak into other dungeons and do them in reverse, taking out the boss first, then his minions, and then the scuts at the door.

The players enjoyed the whole quest line. By the time the last cave was cleared, nearly every one of the players on our roster had been to at least one cave, making it a true team effort. I had planned on making the caves disappear at the end of the quest line, but the players started making plans on what they wanted to do with them, so I guess they’ll become a feature of the town. Of course, they are magically created, so who knows what might pop up in the future…