On the Monster, Random, Wandering or Otherwise

There is so much of our hobby that is obfuscated. It is given, in the rulebook, no explanation, no reasoning, and we are to take it and figure out how it works.

What use are "Random Encounters?" What is the difference between a Random Monster and a Wandering Monster? What is the logistical process of using them in play? How do random and wandering encounters work?

Encounters not keyed to a location exist for several clear and important purposes.

  • Most importantly, they act as a COST for wasteful player behavior. They are the reason players don't just search the room for a fine-tooth comb or just hammer down through any door they can't unlock. 
  • They also Encourage Resource Management, because you have to be able to make it back to town after the adventure. If you go out and cast every spell, just to return to town, you have the wandering monsters on the way back to town and on the way back out. They literally address the five-minute workday problem.
  • They create a Dynamic environment.  The world doesn't sit still and wait for the characters to interact with it; they act as a time structure for adventures.
So, how do random encounters work?

There are Three types of unplanned encounters. Wandering Monsters, Random Monsters, and events.

  1. Wandering monsters are monsters who exist in keyed areas. They monsters are discovered in an encounter, outside of their keyed area. If they are killed, they are likewise removed from the area where they are keyed in the module or adventure.*
  2. Random monsters are just that -- Random. They are monsters from the local terrain, rolled for on the area encounter chart. They have found their way into the dungeon from outside, just like players.
  3. Events are dynamic set-pieces. Think of them as room contents not keyed to any room. They can be any one of a Special Event, Trick, Treasure, Trap, or Interesting Empty Room. My guide for creating these is on the sidebar.
These should be checked for at different intervals. Wandering monsters are traditionally checked for every turn (A segment of time equal to the characters able to move their whole movement safely, usually considered about 10 minutes), but they may be checked for as infrequently as ever three turns. Even more rarely they may be checked once every six turns. Events may be an entry on the wandering monster table.

Random monsters are checked more infrequently. Once every three or six turns is traditional. It is important that there be a check hourly or at some interval that will occur three or four times a session where both wandering and random monsters are checked for. This gives the players to encounter another incursion into the same space they have decided to invade.

Chance for an encounter are traditionally 1 in 6, but may be either more or less frequent. An adventuring party that is efficient and goal directed, in my experience, usually spends between 18 and 24 turns exploring a setting over a 4 hour gaming session. This means that 1 in 6 chance will result in an average of 3 or 4 encounters. Change the die accordingly. A 1 in 8 chance will average 2.5-3 encounters, a 1 in 12 will have 1 or 2.  The type of environment or even the area within the dungeon should affect this choice. Areas of higher traffic should have more frequent encounters.

Allow player action to affect this chance. If my players attempt to destroy a sturdy dungeon door, I usually require between 2 and 3 turns to do so, and roll 3 encounter checks each turn, with encounters on a 1-3. I also usually have the reactions of the monsters encountered trend toward hostile. You are welcome to play your stereo very loudly in an apartment complex at 2 A.M. for an example of the attitudes of people whom you might encounter.

When an encounter occurs, the first action is to roll for distance, then surprise, and then consider line of sight. It is common that players or the monsters might never notice each other and bypass each other completely. Then, when they engage, do not forget to roll for the reaction of the opponents. It is very rarely immediately hostile.

Do not be afraid to take a second to prepare and make the encounter interesting. Not every encounter need be related to the player's quest, but meeting someone with an agenda, speech impediment, or unusual hobby can provide gaming fodder for many sessions.  I suggested Monster Business by Sham's Grog and Blog, and Combat Commentary by Telecanter for starters

* Note that wandering monsters do not explicitly need to be from a specific room -- dungeon patrols and natural denizens who live en masse can be on the table without any additional explanation. In addition to any entries such as the troll from room 34b and "Monsters from the nearest room."


  1. Random monsters are checked more infrequently. Once every three or six turns is traditional.

    In what tradition?

    That is an interesting rule, but not something I have every noticed before in an adventure or rulebook.

    The way I do it, I have one random encounter table for a given zone. Some of the entries are from keyed locations, and if killed or whatever will then not be encountered in their home location, and some can only be encountered on a fortuitous (or unlucky) random encounter roll.

    I'm not sure what is gained by managing two different kinds of random encounter checks at different intervals.

    Here is Moldvay (page B53), just for reference:

    Besides the monsters which live in rooms, characters may encounter monsters which wander about the dungeon. These monsters are known as "Wandering Monsters". At the end of every 2 turns, the DM should check for Wandering Monsters. To do so, roll ld6: a result of 1 indicates that the party will encounter a Wandering Monster in the next turn.

    1. The answers to your questions are in the relevant original sources, and contained in the text above.

      You'll notice that the Moldvay text, conforms to the parameters listed above for wandering monsters.

    2. Do you have a reference in the Gygax DMG or whatever other source you are talking about? Otherwise I'm going to have to perform a linear search on all my old rulebooks, and presumably you were just looking at it for this post...

      Is this what you mean:

      This gives the players to encounter another incursion into the same space they have decided to invade.

      This can happen with only a single encounter check too, either by the random encounter happening while PCs are engaged in a keyed encounter, or by putting X versus Y encounters on the random encounter table as single units.

      Not saying your method is wrong, it just seems like extra work to roll another check every exploration turn when you can fold it into a single check with the same probabilities.

    3. Ok. Sorry it took me forever to locate this text somewhere besides the Hackmaster Gamemaster Guide.

      One of the reasons it took so long to find, is that the wording is reversed. It's on the PHB 1e, page 103.

      "Wandering monsters" are the ones I term as 'random' up above. The text says "a party wandering in the woods. . . might run into nearly any sort of monster"

      Where-as "Set encounters" are "encounters [that] will be in, or near, the monster's (or monsters') lair;"

  2. This is a great post, and particularly relevant both to things I've been thinking about, and to the game I'm currently playing in.


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