Deterministic Encounters, and an Example: The Lamb

February 09, 2024

Random encounters are the famous cornerstone of OSR play. It puts pressure on players by limiting time, and increases overall danger of the dungeon. What would a dungeon be without a random encounter? Boring, and allowing time to dawdle. 

But random encounters have some flaws, I think. For one, they 'just happen,' by which I mean if a random encounter is rolled, the party will... encounter it. I think this disallows opportunities to outsmart an encounter at a higher level, where you know that the 1d6 goblins are wandering around, and you can interact with the goblins indirectly to avoid encountering them at all. For instance, if I want to trap the wandering goblins with a static trap (e.g. bear trap, magical sigil, something else clever), it is not clear how that is resolved with usual random encounter procedures, as the goblins generally do not occupy any of the space outside the encounter. I would like to give this opportunity to outsmart back to the exploration party.

The other flaw I perceive is that it leaves nebulous enemies that cannot be interacted with beyond the random encounter. This is not a flaw of every random encounter system, as many dungeons feature a lair for the enemy, and give a chance of encountering the enemy there. But if you want to hunt or track down where an enemy went, you have to wander around waiting for the correct random encounter to be rolled.

To fix these flaws, I want to propose a different procedure: the deterministic encounter. I think this could be used as a complement or substitute for random encounters. I will also explain how to incorporate a bit of chance into deterministic encounters, should you want it. I thought of this while I ran Lair of the Lamb recently, and will explain how I would implement it in that dungeon. I haven't tried this myself in a real game, so take my thoughts with a grain of unplay-tested salt.

<;" id="deterministic-encounters">Deterministic Encounters

I should start off by saying I don't mean set-piece encounters, by which I mean things the party always encounter, and must encounter to requires a tracking of dungeon turns, or similar time tracking procedures, so keep that in mind.

Deterministic encounters are enemy movements that follow a more-or-less predictable path, like a guard on patrol. An enemy spends 4 dungeon turns in one area, then moves to the next. Then after more turns, it goes back or moves on. You can make a complete circuit that a dungeon dweller navigates, or have a one-way path with a final goal for the enemy (the cultists move from room to room, finally entering the ritual chamber for their last sacrifice). But the key here is that the encounter always occupies a space in the dungeon, no matter the turn.

You could incorporate chance into this easily: destinations could be randomly chosen (or not), and the turns spent there could be randomly determined (or not). It depends on who the enemy is and what they do. 

Ok, Lamb time.

<;" id="deterministic-lamb-encounters">Deterministic Lamb Encounters

I chose the Lamb because I am somewhat dissatisfied with the lowest level's random encounters, especially "The Lamb approaches, full of bile and loathing." It's too much of a random jump scare, and gives no indication of where the lamb is going or doing. All it really says is, "the lamb is here, deal with it," and says this to both referee (figure out what the lamb is doing. Tracking party? Something else?) and player. This can be obviated with some on-the-fly thinking... but after a few of these players will see there's nothing to be outsmarted: the Lamb 'just happens.'

Instead, let's plan a route for the Lamb and give it some turns spent in some rooms. I imagine the lamb doing a whole lot of eating, vomiting, washing, and having some good old-fashioned pit time. So I propose a route as follows, starting from dungeon turn 1 and cycling over at the end:

  1. Lamb moves from Pit to room 1 (Bowls)
  2. Lamb eats noisily and sloppily for 2d4 rounds
  3. Lamb moves to Fountain (1 turn travel)
  4. The Lamb washes itself as best it can for 1d4 rounds.
  5. Lamb moves to Bone Pile (1 turn travel)
  6. The Lamb spends 2 turns vomiting bone pellets and headbutting the wall.
  7. Lamb moves to pit (1 turn travel)
  8. The Lamb does its business, spending 2d6 turns there.

If the party's path crosses the Lamb while moving, they can hear it nearby and will likely encounter it if they do not turn back.

This gives opportunities to outsmart the Lamb: It doesn't enter the eastern half of the lowest level, giving a safe spot to hide. It gives some suspense as the party waits up to 8 turns for the Lamb to finish eating, should they need back into Bowls room. It also gives the lamb a concrete presence at all times, so if the party wanted to hunt it down, they could wander around and find it, or know its schedule well enough to ambush it (e.g. in the pit).

<;" id="flaws-in-the-deterministic-encounter">Flaws in the Deterministic Encounter

You're doing a lot more tracking of movement. If you have more than 3 deterministic encounters in a dungeon level, you might have to pause at the table while managing the encounters. For a truly deterministic encounter (no rolling), the movements and turns could be written in advance and you could cross it off as you progress through turns... but otherwise it can be a bit clumsy.

On the other hand, I think three deterministic encounters is enough for a medium-size dungeon level (20-30 rooms). This gives each encounter space enough to have distinct activities in their route. So maybe this works best with smaller dungeons?

I think this also gets more complicated the more your encounters interact. Yes, they are no longer nebulous 'just happens' encounters, but now if two encounters occupy the same space, you have to decide what happens. The most straightforward way is to roll a reaction roll and adjudicate something. You could also write down ideas in advance. But this is definitely more prep for the Ref than a traditional isolated random encounter.

I also don't know this fits every dungeon; a more mythic underworld-y dungeon may want the unpredictability and nebulousness of 'just happens' encounters. It may fit your dungeon better. I'm simply proposing this for the opportunities to outsmart the enemies, which may not be a thing you are optimizing for. Take this with a grain of salt.

Feel free to let me know what you think. I would love if someone could tell me how this plays out in a real game, either alongside traditional random encounters or instead of them. I plan on trying it soon.

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