In Dungeons & Dragons, there are dungeons. And in those dungeons are doors. Doors were tremendously important in Classic D&D (the term I’ll use to describe the original, B/X and AD&D versions of the game), and I have a few thoughts I’d like to share with you about them, and how you can use them well.

The basic purpose of a door is to divide up a space in a way that the players are not aware of what’s on the other side. This goes both ways – in many cases, monsters on the other side won’t know that the characters are approaching either.

Any door is an opportunity. Whenever my players are engaging in a dungeon adventure, they get very excited upon seeing a door. What’s on the other side? Another corridor is often disappointing. But a room with monsters and perhaps treasure? Fantastic!

A Word on Surprise

In Classic D&D, two opposing forces – monsters and the adventurers – would meet. And, by the standard rules, a 1d6 was rolled for each side. On a roll of 1 or 2, that party was surprised and could not act in that first round. (In AD&D, things got complicated. I ignore those rules and use the original ones).

Surprise is still a concept in D&D 5E. Instead of rolling six-sided dice, the idea is that potential combatants roll Dexterity (Stealth) checks and compare to the opposition’s passive Perception scores. If a combatant starts a battle unaware of everyone on the opposing side, then they are surprised. These rules can get a little bit fiddly.

There are situations when the DM rules that one or both sides cannot be surprised. If both parties are approaching down a long corridor and holding light sources and being noisy, no surprise for anyone!

Doors, however, block light and sound. And so, the potential of surprise returns!

Listening at Doors

In Classic D&D, most parties would listen at doors before opening them. Why would they do that? Well, if they could hear a monster on the other side, the party couldn’t be surprised! It makes sense, doesn’t it?

Classic D&D assigned superior chances to hearing noise to high-level thieves and non-human races, for everyone else, a 1 on 1d6 indicated that noise was heard (if possible).

In D&D 5E, a character can make a Wisdom (Perception) check against a DC set by the DM. DC 15 is a good standard; if the monsters on the other side are particularly stealthy, I’d set it at DC 15 + their Stealth bonus. (Hearing sounds through a door is more difficult than if the door isn’t present!) Yes, this is a use of a passive Stealth check.

Once you’ve heard something on the other side of the door, you can’t be surprised! Hooray! But do you surprise the (unaware) monsters?

Opening Doors

Classic D&D had a trick to counteract the benefit of listening at a door. You see, all dungeon doors were typically stuck, and to force open a door a character had to roll a 1 or 2 on a six-sided die. Typically, I would allow two people to simultaneously attempt to open the door: if either rolled successfully, the door opened first time.

If the door didn’t open, then the monsters on the other side were alerted, and so couldn’t be surprised. If the party had failed their Listen checks, they were the only side that might be surprised!

In D&D 5E, opening a stuck door is a Strength or a Strength (Athletics) check (typically I use the latter), with a DC of 10 or 15, depending on how I’m feeling. The penalty for failing is the same as before.

You can attempt to force open a stuck door multiple times; failing once doesn’t mean you’ll fail the next. The penalty for failing – alerting those on the other side – remains. Each failed attempt grants them another round to prepare.

Once the door is open, if both sides remained unaware of the other, D&D 5E is mostly silent on what happens. In Classic D&D, you’d make a surprise check for each side that was unaware. In D&D 5E, either I rule that neither side is surprised, or I require Stealth checks from everyone. (Which probably leads to no-one being surprised). I do the former far more often than the latter.

But the twin check of Listening and then Opening a door provide tension and the possibility of changing the initial state of an encounter.

In 5E, if one side is aware, that side could make Dexterity (Stealth) checks against the passive Perception scores of the other side to potentially surprise them.

Locked Doors

Any door that you designate as Locked should be one you’re happy with the players not opening. Or, if the design of the dungeon requires it to be passed, an alternative way of opening it is required. You can put a locked doors in front of a special reward that rewards those who came prepared to deal with locks. Or to require the players to explore more of the scenario until the find a way of opening the door.

Doors can require a key, a puzzle solution, or a lever elsewhere in the dungeon to open. (There are plenty of this latter sort in Elden Ring, if you’ve played that game).

A standard locked door can be opened with a set of thieves’ tools and a successful roll with someone proficient in them. I do not permit additional attempts by the same character: Either they are good enough to open the lock or they are not. (If they gain a level of experience, they can try again).

Some doors made of flimsier material can be broken open, with a higher DC than to get through a stuck door. I would use a DC of 15 or 20 for doors that I wanted to entertain the possibility. Again, this is a one-chance-only check. You can’t keep trying until you break down the door.

Secret Doors

Much as locked doors, but more so, secret doors are typically ones that you don’t intend players to find. They lead to special areas of the dungeons and rewards. When they are necessary (there are some in Tomb of Horrors, for instance), they’re part of a puzzle design: can the players find all the secrets to complete the dungeon?

Yeah, Elden Ring and a lot of other computer games have secret doors as well! (I mention Elden Ring just because I’ve been playing it recently. A Bard’s Tale had secret doors. There are likely earlier games as well).

The main challenge with a secret door is finding it. Not only do you need to roll a check successfully, but you also have to look in the right spot. And search for secrets in the first place!

Putting a secret door at the bottom of a pit trap is being sneaky.

Some adventures allow characters to find secret doors by just saying where they look. The more common way is for the characters to search for some period of time and make a roll.

In Classic D&D, a roll of 1 on 1d6 detected a secret door (a 1 or 2 for non-humans!) Searching typically took 10 minutes. AD&D complicates things a lot but running it in 10 minutes is a lot easier. In the old terminology, ten minutes is one Turn. In So You Want To Be A Dungeon Master, Justin Alexander refers to this measure as a Dungeon Turn, because the term “turn” has its own meaning in D&D 5E.

It seems a good use of the terminology, so I’ll also use it.

In D&D 5E, typically DMs allow you to find secret doors with successful Wisdom (Perception) or Intelligence (Investigation) checks, choosing one or the other depending on their mood and what the scenario says. These days, I allow characters to use either. A typical DC is 15.

Searching, Time and Wandering Monsters

There is no penalty for failing to find a secret door. You can retry as many times as you like. The only thing you’re expending is time. (And oil/torchlight, if you track those things. Most people don’t.)

But if you’re only expending time, then what stops you from checking until you succeed? Especially when you know there must be a secret door there.

This is where another aspect of Classic D&D comes in: the Wandering Monster check.

The original form is that every Dungeon Turn, the DM would make a roll of a six-sided die. On the roll of 1, one or more wandering monsters would turn up. Various scenarios changed the frequency of checks or how often they “succeeded”. A chance of 1-2 on 1d6 every two Dungeon Turns. A 1 in 1d8 chance ever three Dungeon Turns.

The point of having these checks is not only to provide the illusion of a dynamic environment, but also to provide risk for activities that take time. If you’re running a dungeon, I strongly recommend you have wandering monsters. (That so many recent dungeons don’t include them, especially the larger ones, makes me sad).

You can see how all these concepts fit together. Doors provide opportunities, risk, and rewards in the game. But a few relatively simple concepts are used to make everything tie together and provide meaningful decisions for the players. And meaningful decisions are what I want out of a game of Dungeons & Dragons!