The Whens and Hows of Random Encounters

Role-players have always had a love-hate relationship with Random Encounters. Back in the day they were always used, but as the game became more advanced, the Dungeon Masters tended to do away with them. Recently, since the resurrection of the classic gaming style, many DMs have decided to include them in their play style once again. The problem that can arise now is that it is kind of a lost art.

Above ground, Random Encounters aren’t so hard to figure out how to handle. All you have to do is judge how long the party is going to be traveling, and then check the tables for the area that they are in. Below ground, however, is a completely different subject. While much of the time spent traversing wide open spaces is pretty much unaccountable for, each moment spent underground IS accountable. For this reason dungeon masters had to figure out ways of measuring time.

Time in 2e is measured in units of rounds or turns. For reasons of simplicity rounds are about a minute, sometimes shorter and sometimes longer but for purposes of tracking time we will always assume that they are a minute. Turns are roughly ten minutes. This unit of time is only usable during fights, but what about when they are exploring? Well, for times like this we must assume other things.


Typically, in modules which use random encounters, they will list how often that random encounters are to be checked. Often it tells you to check for random encounters ever turn, which is ten minutes. There is another thing which old-timers have taken for granted, and without this little clue about time keeping, you are in a world of confusion. This little known clue is that once a party enters an underground dungeon, or a building which is a big part of the dungeon, the units which we use are changed. Instead of time being abstract, we change this logic to Dungeon Time = real-time. This will float, and it really isn’t the same as real-time, but for time itself we assume that each session = 1 day in game time. Thus, wizards who run out of spells are out of luck until the next game unless they can convince the party to take them above ground, or back to town to let them rest and memorize new spells.

Now then, with this understood, if you would like, you can go out and purchase one of those cooking timers, or borrow your wife’s but for reasons of personal safety, it is best that we return it once we are done using it. If the module has dictated that we should check for random encounters every turn, then we set our timers for 10 minutes, and when it goes off, the players all go silent and look at you expectantly while you roll percentile dice for some reason which they may or may not understand exactly what it is for.

With that said, many factors can affect how often we check for random encounters. In combat which is either pre-set, or listed in the key, the moment that the players enter the room, we must subtract the number of minutes which has expired from the Random Encounter Check time.

As an example, we know that there are 4 trolls in the room which the party has just entered, we look at our timer and there is still 5 minutes left to the random encounter check. This means that we now ignore the timer and instead judge the number of minutes in rounds. Thus in 5 rounds we will check to see if a random encounter has happened.


The percentage listed (if we are going by percentages) assumes that the party is being quiet as possible. This doesn’t factor in noisy armor which we must determine how noisy the armor is if someone is an idiot and wearing full-plate armor in the dungeon. Perhaps a fair modifier to the percentage chance of attracting a random encounter is +25%.

Loud noises, such as bashing in a door, setting off alarms, or the loud clanging of weapons striking armor, and the yelling and screaming involved in combat is very likely to call attention to one’s location. These instances will increase a party’s chance of being discovered by a random encounter considerably! +50% sounds like a fair modifier to me.

You must always be aware of a noise level, bashing in a door worth 50hp takes time and makes a lot of noise. It also allows those on the other side of the door to prepare themselves and take appropriate action. A quiet castle will be on low alert as long as the party uses stealth and wisdom in moving around, but once it is discovered that the walls have been breached, all of the guards and monsters will be on high alert. This also factors into Random Encounters.


A way to cut down on the amount of dice that you are rolling is to change the way that you check for them. Many times a percentage number is given, but we can also use a d20. During our prep we assign which monsters we want to have running around our dungeon. The lower the number the more of these creatures will be running around. The mid-numbers, say 8-11 can be limited, if the party defeats these creatures they will be depleting the monsters from a limited supply which is normally found elsewhere in the dungeon level. Say a snake that normally can be found in room A43 on the Dungeon Key can be encountered randomly, if they kill it before finding its lair, then once they get to room A43 there will be no encounter in that room, also, if they already killed the snake in its lair, then there will be no random encounter. The higher numbers always represent No Encounter.

Another method of checking for random encounters, which is much easier then rolling percentile dice is to just use a d6 or some other die. Prior to play we must decide what is the base chance of having an encounter, say, 1-3 results in an encounter, and this number can float up or down depending on how the players are acting. Loudness or engaged in noisy combat will give the odds of an encounter to 1-4 or even 1-5 on a d6, but we can also improve this by allowing a thief to lead the party, making it 1-2 on a 1d6 to dictate encounters.

Use your imagination, but remember to keep it fair and logical. You can have all of the monsters on the Random Encounter list to be limited, or have them not have any effect on the dungeon population at all! Random Encounters are used to add depth and richness to the world, they can also be dangerous! Don’t be afraid to judge them properly, if a party has had the crap kicked out of them, they may be worth more to the villain alive then they are dead. An incredibly powerful party will cause fear, the random encounter could run away and alert those around them to the powerful parties presence in their lair. Just because something is random, doesn’t mean that it doesn’t have to make sense.


Rob Green said...

There was a random encounter idea in an old Dragon. I think it was thus. You have a random encounter stock (which could be the same as the dungeon stock.) Each encounter is given a number from 1 to 20 (seeing as you are supposed to have 10 encounters per level make it 1 to 10.) To decide if you have an encounter roll d20. Whichever encounter you roll you get. If you beat it they never come up again. So at the beginning you have a 50% chance of an encounter, but as you chip away at them the chance gets less and less as you deplete the stock.

DMWieg said...

I find that I am particularly stringent when it comes to wandering monster rolls inside dungeons. I find that this cuts down on the party camping out in every room, which is one of my personal pet peeves as a DM.

On the other hand, I tend to gloss over random encounters if the party is traveling in relatively settled lands. (Or at least the random encounter roll is just to see if they pass some travelers on the road.)

I have played in games where random encounters are done by the book, and I find that without at least some DM fiat it makes the game cumbersome and tedious. As you said, it is something of a lost art.

Anonymous said...

I don't know about the "real-tim = game time" in dungeons, I haven't heard about that.

What I do know is that random encounters were a punishment (incentive?) for inefficient play. So if the party wanted to stop and rest after every battle because the Magic-User blew every single spell he had, that's fine. The DM just rolls for a bunch of random encounters.

In your egg timer method, you're really saying that there will be X chances of a random encounter this session because that's how long we spent exploring the dungeon. But when you're in a fight you track by round and stop the timer. So there's an incentive to fight a lot. In fact, if you can hold off on killing that last goblin until the thief finishes solving this puzzle, we save a random encounter check or two. That sort of thing.

But random encounters were a penalty because they didn't carry treasure, and most XP came from treasure. Random encounters were dangerous and time- and resource-consuming without much reward.

Used in that fashion, you can use random encounters based on in-game time spent (once per turn seems a bit much to me, I'd say once per half-hour in a crossroads area or per half-hour elsewhere).

Or you can just do why my first DM did and roll whenever everyone at the table is sitting around wasting time arguing. At that point a random encounter is still a penalty for poor play, but it's poor table-play instead of inefficient use of character time in the game.

The distinction goes like this: poor table play involves a lot of planning and arguing and blah blah blah, which is sometimes good and sometimes too much. The DM can make a judgement call when he thinks things need to move on. Get a bored look in your face and idly roll dice every couple minutes. Players will get the hint.

But poor efficiency in the game world involves things like wasting time searching every square, carefully picking a lock instead of bashing it down (which may be a good choice sometimes), spending time camping because you spent your spell resources (which stems from poor combat tactics), getting lost due to poor or no mapping, etc.

RipperX said...

See, 1d30, I completely disagree. To me, it adds randomness into the game. The dice decide if the players are interrupted, and by what. There are great monsters that work best as roaming monsters, and while the random encounter method is not 100% accurate, it sure as heck beats trying to track the movements of everything in the dungeon.

It would be interesting to find out the other reasons that DMs have brought back Random Encounters into their games.

AndreasDavour said...

I used random encounters in my 3rd ed game, and since murder is the only real source of xp in that edition they advanced like lightning. Bad. I halves xp for random encounters.

Clock!? I thought you had those movement rates for a reason. The characters move 40' down a corridor? Just look at the PC sheet to see how long it took. Way easier than playing real time.

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