The Keep on the Borderlands 2025 Sessions - The One About Mechanics

This post is about some of the mechanics I use in Keep on the Borderlands. This module was contemporaneous with AD&D and came out just a bit before the Expert Boxed Set. No one would have had those rules at the time of B2’s publication, which creates all sorts of oddities. I personally use Old School Essentials by Necrotic Gnome over the original Basic and Expert rules because I was able to obtain them in hard copy. As of right now, the B/X rules are available in POD, so I will probably order these for nostalgic reasons. 

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Looking at the module, the map scales are poor. The Caves of Chaos combine both interior and exterior maps, but the transition between them is awkward. The interior maps are fine, yet the valley floor is a ridiculously tight space. I’ve covered these complaints elsewhere, and none of them are deal-breakers. I simply ignore what I want or come up with reasonable rules of thumb. About 99% of these adjustments favor the players, so they don’t object either.

The second issue is the wandering monsters. Every area lists specific wandering monsters, then claims that no reinforcements are possible. Elsewhere, the text mentions that new monsters will move into cleared areas of the caves. Some versions of the module even include a wandering monster table completely different from the earlier lists. What a mess! All of these ideas contradict one another.

Here’s what I do with these conflicting rules: I condense all the wandering monster lists down to creatures that actually appear in the module. Four times a day, I roll for wandering monsters: Sunrise, noon, sundown, and midnight. If the result matches a group that has been depleted, I treat it as reinforcements for that group’s location. 

If I roll a monster type that hasn’t taken losses, I use the reaction table. If the result is neutral, the newcomers move on. If it’s positive, they join the home team. Even if there are no losses to replace. They are evenly divided among all relevant locations. If the result is hostile, a fight breaks out between the newcomers and the cave’s inhabitants. I don’t bother running the combat; I simply roll damage for both sides. Nine times out of ten, the newcomers are wiped out, leaving their gear and treasure behind for the victors. Oddly, if there is a net loss of monsters, the survivors come out on top because they have better gear and treasures. 

The fun part is that the players get unpredictable new encounters without knowing where these monsters came from. Just like you. I’ve been rolling for reinforcements through all nine sessions so far, though I hadn’t mentioned it in my posts until now. 

There’s one catch to all this: you only roll while the game is in session. If a session lasts a day, that’s four rolls. If a time break occurs, for example, if the party retreats to the Keep, you don’t roll for that downtime. Rolling for every day that passes, regardless of player activity, would flood the area with monsters. Wandering monsters should be a randomized response to player action; if the players are inactive, no roll should be made.

The party has been here for 5 days, for 20 wandering monster rolls. Monsters are rolling into the area due to all the strife. Here are the results, in order of appearance: 

Giant Rats (4), Owlbear (1), Kobolds (10), More Rats (5), Goblins (3), Goblins (6), and a group of traders. 

The rats and Owlbear all gravitated to Cave G, more than restoring that area. The party saw this happen, but missed the rats. The goblins and kobolds went to their known haunts and became reinforcements; the party probably saw this, but didn't understand these were new creatures and not the remaining survivors.  

I decided to give the trader a chance to live by generating a party traveling with a high-level magic user. You can use the same generator here. I then deleted every character over the second level, leaving 6 characters. 

For this run through the Caves of Chaos, the players did something unusual. They haven’t really fought the kobolds. Kobolds are generally weak and tend to attract player aggression. I’ve played them as opportunists, striking only when the players seem weak or distracted. Since I’ve run this module half a dozen times before, I wanted to avoid another head-on clash with the kobolds. I already know how that plays out.

The next session will start with the appearance of the wander party. 

If you like the goblin and kobold figures, you can find them in your local hobby shop or perhaps on Amazon, here and here. They even have an Owlbear. As an Amazon Associate, I earn from qualifying purchases.