Master the Dungeon – how to handle Traps, Secret Doors, and Hidden Monsters in 5E D&D!

In the first article in this series, we looked at all the many problems with how Perception works in 5E – and when and how to use the Perception skill in general. If you haven’t read that article yet, you may want to do so – but if you’re just here to figure out how to deal with traps, secret doors, and hidden creatures in 5E, well then that’s what we’re going to delve into now.

Speaking of delving, make sure you check out DELVE, a complete guide to building and running dungeons – it’s a project we’re making with Bob World Builder and the catalyst for this article series on Perception and dungeon exploration.

DELVE is a 200+ page sourcebook for both 5E & Shadowdark published by Eventyr Games and Bob World Builder, which features 10+ dungeons, 40+ monsters, 40+ magic items, 40+ traps and hazards, new dungeon-inspired player options, and more!

As I concluded in the previous article, Perception checks are way overused in 5E Dungeons & Dragons. Almost 90% of the time, you don’t need to call for a Perception check, because things are easily perceivable either at a glance or with close examination. The GM should only call for Perception checks when there’s a chance of failure AND consequences of failure.

Surely, however, that means that the GM should call for Perception checks when it comes to traps, secret doors, and hidden foes, because there are obvious consequences here, right?

Well, yes and no. Let’s take a look at each in turn!


Probably one of the most repeated questions in a dungeon is: “Can I check for traps?”

Traps can be tough to handle. It doesn’t help that 5E has been inconsistent with how traps are handled. In the first modules, designers leaned heavily on Passive Perception, where a character would automatically spot a trap if their Perception + 10 was higher than the trap’s DC.

That’s an easy way to handle traps that eliminates the metagaming issue (when you call for a Perception check you reveal that there is something to be perceived – which Passive Perception fixes by not calling for a check) without slowing down the game.

Unfortunately, it’s also quite boring, as the GM knows exactly which traps the characters will find and which they can’t find. Which is also why we’ve seen a move away from Passive Perception in recent years – but that comes with its own problems, because if the GM or the players constantly ask for Perception checks, the game is slowed down and metagaming can become an issue.

So what do you do?

Essentially, my advice is that you give characters two options when looking for traps:

Examination – a character can choose to get close enough to touch and spend a few minutes to search an area or object of about 5 cubic/square feet. If they do, they treat it as if they had rolled a 20 on their Perception check for that area.

Last Second Spot – if the character is just about to trigger a concealed trap, they get to make a Perception check against the trap’s Find DC (as long as they’re not distracted or rushing). On a success, they spot it just before triggering it. On a failure, they walk into the trap – oops!

The idea here is that clever and careful examination will usually find traps – but it requires explicit thought, is time consuming, and might be dangerous because the character has to get close. So it’s something the characters are likely to reserve for when something looks suspicious or out of place.

But that doesn’t mean that they’ll blindly walk into every trap they don’t actively search for. The Last Second Spot rule gives characters a chance to avoid traps at the last second. And, because failure triggers the trap, there’s no meta-knowledge revealed.

By using these two rules, there’s no unnecessary rolls, no meta-knowledge revealed, and both clever players and perceptive characters are rewarded. Win-win!

DELVE has 40+ traps and hazards for 5E D&D and Shadowdark RPG!

Using Investigation

You might be asking: What about Investigation? Isn’t that for finding traps?

We discussed this in more depth in the last article, but in summary, Perception is for sensing stuff and Investigation is for making sense of stuff. So, actually finding the trap (or part of it) uses Perception, but figuring out how the trap works, how to avoid it, and how to disarm it (or even that it’s a trap at all) uses Investigation.

It’s a simple difference – Perception lets the character find the slightly raised tile in the floor. Investigation lets the character deduce that it’s a pressure plate that mechanically triggers something elsewhere in the dungeon, how much pressure must be applied to trigger it, and how it can be jammed so it doesn’t trigger.

Note that in some cases, especially when it comes to magical traps, other checks like Arcana or Religion may be used instead of, or in combination with, Investigation.


Here’s a quick example of how finding traps might look in play.

GM: You enter a long hallway with doors on either side. Spiderwebs hang from the ceiling and the floor is covered in dust.

Bob the Barbarian: I’d like to check the hallway for traps.

GM: Checking the entire hallway carefully for traps would take you a few hours.

Bob the Barbarian: Well, we don’t have that much time. Can I just stay on the lookout for traps then?

GM: Of course. You proceed down the hallway, staying aware of your surroundings. As you near the center of hallway, I need you to make a Perception check.

Bob the Barbarian: That’s a… 17.

GM: You notice that there are faint burn marks on the floor about five feet ahead.

Bob the Barbarian: There’s burn marks up ahead, guys.

Winny the Wizard: I’d like to examine the burn marks up close.

GM: You approach and spend a few minutes carefully examining the burn marks. Give me an Investigation check.

Winny the Wizard: That’s a 23.

GM: By the angle and spread of the burn marks, you deduce that they came from above. Looking up and examining the ceiling, you find an almost imperceptible glyph there. Give me an Arcana check.

Winny the Wizard: And it’s a.. 12.

GM: The glyph is obviously magical and seems active. It creates a fiery blast when triggered but you unfortunately can’t tell what would trigger it. You know it can be suppressed with a Dispel Magic spell.

Secret Doors & Hidden Treasure

Secret doors or hidden treasure – stuff the characters want to find, but can’t easily spot – is another matter.

Because you don’t “walk into” a secret door, the Last Second Spot rule won’t work, and, if you ask for a Perception check when a character walks past a secret door, you’ve revealed that there’s something to be found here, even if they fail the check.

So what do we do?

It’s quite simple, luckily. To find a secret door (or another hidden, non-dangerous object), a character has to examine the area where it’s in. Get close, spend a few minutes, chances are that they will find it (lets say the secret door has a Perception DC of 20, so any character with a +0 or higher in Perception would find it by examining the area closely).

The issue, of course, is that the players may feel that they have to examine everything to find secret doors then (which is tedious for everyone involved) or just give up on trying to find secret doors altogether.

This, however, is an issue that the GM can fix, by making sure that they give hints to where a secret door might be found. Whether that’s emphasizing the description of a mural or noting how tracks suddenly disappear by the wall, there are plenty of ways to drop hints to the players.

In addition – and this is important – the GM should never hide something the characters need to find, unless they’re certain that the characters can actually find it. Secret doors are best used as rewards for players that are inquisitive, so that thinking to look for a secret door yields an easier way to the villain’s lair – but not the only way.


Below is an example of how you can telegraph the presence of a secret door in a way that won’t reveal outright that it’s there, but gives the players a fair chance to examine the area more closely and finding it.

SCENARIO: There’s a hallway with a secret door, which is opened by pushing on a mural of a knight mounted on a dragon.

NO HINT: “The hallway is 30 feet long.” [The characters haven’t got the slightest clue that there’s a secret door here]

HINT: “The hallway is 30 feet long. Murals fill the walls, showing scenes of dragons in flight.” [The characters are aware of the mural and may choose to examine it closer]

STRONG HINT: “The hallway is 30 feet long. Murals fill the walls, showing scenes of dragons in flight – halfway down the hallway, a knight seated on the back of a dragon looks to be holding a glowing sword aloft in triumph.” [The characters are explicitly steered toward the exact spot where the secret door is]

Hidden Enemies

Finally, there are hidden enemies – ambushes in the dark, a monster stalking the party, and so on.

This is where Passive Perception really shines. It’s really easy to roll a Stealth check for a monster, measure it against each characters’ Passive Perception, and use that to determine who notices the monster and who doesn’t.

When it comes to ambushes, it is also perfectly valid to have the players make Perception checks against the monsters’ Passive Stealth (Stealth + 10) just before the ambush takes place, if you want the players to make the rolls. That’s really just a matter of preference – but there’s no need for Perception checks, unless you want to make them.

In short – don’t make hidden foes and ambushes complicated. Monsters roll Stealth checks vs. the characters’ Passive Perception. That’s it. Easy.


That about wraps it up – and, hopefully clears it up too. To summarize (because who doesn’t love summaries), here’s how I suggest you handle traps, secret doors, and hidden foes in your 5E:

  • For traps, characters must either specifically examine (get close, spend a few minutes) the area where the trap is (getting an automatic 20 on their Perception check) or they get to make a Perception check to spot the trap just before it’s too late, triggering it on a failure.
  • For secret doors, don’t ask for Perception checks but hint at their presence. To find them, the players must pick up on your cues and examine further!
  • For hidden enemies, roll Stealth checks against the characters’ Passive Perceptions – or the other way around, if you prefer.

Traps, secret doors, and stealthy monsters are, of course, only some of the elements found in a proper dungeon – so, if you’re itching for more tools for building and running awesome dungeons, make sure you check out DELVE!

DELVE is a 200+ page sourcebook for both 5E & Shadowdark published by Eventyr Games and Bob World Builder, which features 10+ dungeons, 40+ monsters, 40+ magic items, 40+ traps and hazards, new dungeon-inspired player options, and more!

That’s it, so until next time, may your dungeons be deep and filled with treasure!

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