Dungeons & Dragons began in the dungeon. It’s the form of the game that I keep returning to, because dungeons are cool. They provide an environment that allow the players to make interesting choices, whilst allowing the DM to easily understand their structure. With the release of Tales of the Yawning Portal, we’ve been given seven classic dungeon scenarios to play with.

I’m a very big fan of having wandering monsters (also known as random monsters) appear in dungeons. The idea with a wandering monster is to keep the characters on their toes, and to remind them that the dungeon is a living place with monsters going about their business (or patrolling to see if there are any adventurers causing problems!) You’ll find that many of the dungeons in Tales have wandering monster tables.

Wandering monsters work like this: You make a check on the table whenever a certain amount of time passes.

In original D&D, it often worked like this:

• Every 10 minutes, roll a d6. On a 1, a wandering monster encountered the party.
• Roll d% on the wandering monster table to discover what monster is encountered.

In newer D&D adventures, it often works like this:

• Every 1 hour, roll a d20. Use the encounter on the wandering monster table. (A range of values, such as 1-10, are listed as “No encounter).

I like using the original method when there is a wide range of monsters that might appear, but the modern method typically works well. Note that you can entirely change the frequency of the checks, along with the chances of having an encounter. Want to make an encounter occur on a 1-2 on a d6 every 10 minutes? Go for it!

Wandering monsters increase the danger of the dungeon, and have a tendency to derail an adventure’s plot if too frequent or deadly. One of the major effects of wandering monsters in the new edition is to prevent characters from taking short rests. It’s rather hard to spend an hour resting when monsters attack every half-hour! This can have a severe effect on the effectiveness of certain classes, especially the warlock, which depend on taking short rests. I typically want a balance between the two extremes: short rests whenever the characters want, or no short rests. One short rest per expedition sounds about right. There are two ways of handling this. One is making the wandering monster checks “fail” with a frequency that gives some chance of resting the hour. The other, which is the method I prefer, is to designate certain rooms in the dungeon as safe areas to rest.

The other side of running wandering monsters is working out how much time passes as the players explore the dungeon. This is something that I typically handwave (it feels like you’ll have spent an hour, so let’s make a new wandering monster check!), and it’s something that isn’t really covered in the current rulebooks. Yes, you have a travel speed (typically 200 feet per minute if moving stealthily), but how long does it take to search a room? Much of that is left to the Dungeon Master to determine.

I tend to fall back on the older forms of D&D to track these durations. In original D&D, the “turn” meant something different than it does today. The “turn” was 10 minutes duration, and was used during exploration as a useful abstraction of time. How long did a combat take? 1 turn. How long did it take to explore a room? 1 turn. Indeed, combats would only take 2 or 3 minutes (or even less in Basic D&D, with its 10-second rounds), but you’d call every combat “1 turn” because it was easier to track. I typically make check marks on a piece of scrap paper to keep track of time, making wandering monster checks as appropriate.

One big difference between modern D&D and AD&D is the speed of characters when exploring. In AD&D, a group of characters with one player in plate mail would explore (and map) 60 feet of corridor every ten minutes. If they weren’t mapping, they moved at ten times that speed: 600 feet every ten minutes. In modern D&D, a group of characters can travel 2000 feet in that time!

So, to use the “exploration turn” (or 10 minutes) as a useful abstraction, you could say:

• Movement between rooms (including listening at doors & mapping): 10 minutes
• Dealing with the contents of one room (exploration & combat): 10 minutes
• Role-playing: 10 minutes+ (depending on actual time spent).

If the characters are progressing down a lot of tunnels without entering rooms, work out a distance after which 10 minutes passes. Say, every 300 feet. Or 2000 feet. Or 60 feet.

Why do it this way? Because then it’s easier to track how much time has passed, which is important for those wandering monster checks! (Or when the group gets tired and needs to rest, or when their torches/lanterns run out!) I use check marks in groups of six (rather than five) – each six is an hour – making it easier to read.