Failed Perception/Knowledge Checks

[Draco_Lord]

So, as a DM I really don't like blindsiding my players too too much. At the same time, I don't want to sign post every trap, hidden monster, fake room, and so on. I usually try to have some kind of skill check that can provide hints.

A simple example would be lets say I have a room with a dangerous trap inside of it. Across the room is a door. The door is reality is a fake trapped door, put there to fool adventures who want to teleport across the room. The real door is hidden 10 feet to the left.

In this situation I would ask the players to make a perception check, a knowledge engineering check, or something to that effect. The problem I'm having is that my players sometimes realize that it means there is something up. So I'm looking for ways to hide the fact they failed, maybe give some other information, or things like that. Rather then say they don't see anything.

I understand this is general, so general advice is fine to give.

[Geddy2112]

Make rolls in secret. I keep my PC's perception, sense motive, bluff and sleight of hand stats handy so I can roll them and if a PC succeeds then I let them know. This also lets you keep track of passive/take ten rolls so PC's don't have to roll perception to see that it is sunny, that the bar is a bar and other checks that would fall into zipper DMing.

You don't have to grant rolls to players either. If they don't ask then they can blindly march up to the door/trap/gelatinous cube.

[Draco_Lord]

I should start recording their throws. Slight pain, because everyone levels up between sessions, and I'd need to ask. But I can always just start inferring things, ask for the roll and the result for instance. Or have them message me.

I don't always do that. I don't ask for it if they see a monster, or are charging at something without thinking. But I do feel that if someone with engineering ranks sees a bridge, they should get a free check to see if it looks stable.

[Ashtagon]

This is a variant of the "trap problem".

The trap problem is that traps aren't interesting. There are four permutations:


Not detected, not triggered: This is not interesting.
Not detected, triggered: This is basically a hit point tax. Not fun.
Detected, not triggered: The rogue did his job.
Detected, triggered: The rogue half-did his job.


The key point here is that traps only become interesting if they are detected. In terms of dungeon design, this has certain consequences:

1) Don't place traps except in locations where players might reasonably expect there to be traps. Otherwise, you get the problem of them checking for traps every ten feet "just in case."
2) Make the traps easy to detect. Knowing the trap is there should be the easy part.
3) High DC Search checks should be reserved for when the PCs know something is hidden, but not where exactly (cf. the purloined letter (https://en.wikipedia.org/wiki/The_Purloined_Letter).

With regard to point #2, remember there is a big difference between "I think the chest is trapped", and knowing what kind of trap is present. The Search check could be to identify the nature of the trap, rather than the fact that "something is off about this trapped thing".

For your door, you might say that it is a DC 10 task to notice something looks odd about it (so basically anyone who takes full round action to ask will notice, anyone who takes a look around the room while not engaged with hostile will notice, and dwarves will always notice, assuming stonework is involved), DC 15 to determine that it is a fake door, DC 20 to determine that opening the fake door triggers the trap in the room. Once they've determined that the door is fake, they might reasonably decide to start searching for hidden doors.

The point here is, noticing something is "off" should be easy. The point of a trap shouldn't be to take hit points away by being triggered. The point of a trap, for game-play purposes, is to be interacted with.

[Hrugner]

I like to prop up these sorts of checks with close skill defaults. You get your spot check, but can make a knowledge check to beet a DC 5 higher for similar information. Spot lets you see that the door is fake, dungeoneering would tell you a door really shouldn't be there.

I'm not sold on Ashtagon's traps are boring rule. Your example pretty easily shows that the trap is there to indicate that whoever built this dungeon is aware of teleportation as a method of bypassing threats and that they likely have further anti-magic plans in store for the player. After the anti-teleport trap you're free to put traps that trigger on detect magic, excessively flammable rooms anti-magic fields, lead lined rooms, and other similar events having given the player fair warning.

[Psyren]

Traps that are difficult to detect can be engaging too. After all, what you're doing there is creating a situation where the rogue gets to shine. The key is moderation, or better yet, getting creative to involve the rest of the party.

For example, I could envision a standard pendulum blades trap going down a narrow corridor, the rogue has to find and disable them in sequence and they reactivate two rounds later for instance. Well, under normal circumstances you can get the whole party through by having them pass each row of blades one at a time - only the rogue gets to roll there, so it's boring.

But you can easily spice it up by throwing in some scavengers to attack the party while they try to traverse the corridor. Bonus points if the scavengers are creatures that are less at-risk from a trap itself - for instance, let's say ochre jellies, that are there to feed on the remains of any creatures that fell prey to the blades. Now the rogue is under pressure and needs Skill Mastery in order to take 10, increasing the likelihood that he'll fail and a party member might either get hit by an unseen blade, or be forced to hang back. And the jellies themselves, being mindless, surge through the trap heedless, and every blade that hits them causes them to split and multiplies the danger to the party.

[Nibbens]

maybe give some other information,

This!

To use your example, ask your pcs to do the perception check - they roll well, but fail to hit the DC - I'd describe something in the room other than the door. How about, they notice a small trickle of water coming down from the roof onto a small pool in the corner of the room. This stagnant water is the reason for the mildew smell emanating throughout the room.

This description will throw them off the scent of the "something's up." Also, do this a few times when there is nothing important (maybe just some fluff or detail about the environment) and your PCs will never know when something important was gained or missed.

Note: By doing this, you may actually have to come up with more details for your own descriptions if the PCs press too hard - and maybe this will lead to some interesting interactions or facts that you didn't even know about when you were originally designing the dungeon.

Also...


This is a variant of the "trap problem".

The trap problem is that traps aren't interesting. There are four permutations:


Not detected, not triggered: This is not interesting.
Not detected, triggered: This is basically a hit point tax. Not fun.
Detected, not triggered: The rogue did his job.
Detected, triggered: The rogue half-did his job.


The key point here is that traps only become interesting if they are detected. In terms of dungeon design, this has certain consequences:

1) Don't place traps except in locations where players might reasonably expect there to be traps. Otherwise, you get the problem of them checking for traps every ten feet "just in case."
2) Make the traps easy to detect. Knowing the trap is there should be the easy part.
3) High DC Search checks should be reserved for when the PCs know something is hidden, but not where exactly (cf. the purloined letter (https://en.wikipedia.org/wiki/The_Purloined_Letter).

With regard to point #2, remember there is a big difference between "I think the chest is trapped", and knowing what kind of trap is present. The Search check could be to identify the nature of the trap, rather than the fact that "something is off about this trapped thing".

For your door, you might say that it is a DC 10 task to notice something looks odd about it (so basically anyone who takes full round action to ask will notice, anyone who takes a look around the room while not engaged with hostile will notice, and dwarves will always notice, assuming stonework is involved), DC 15 to determine that it is a fake door, DC 20 to determine that opening the fake door triggers the trap in the room. Once they've determined that the door is fake, they might reasonably decide to start searching for hidden doors.

The point here is, noticing something is "off" should be easy. The point of a trap shouldn't be to take hit points away by being triggered. The point of a trap, for game-play purposes, is to be interacted with.

This. Knowing something is off or odd about a trapped item should be a dead give away - but knowing exactly what it is requires the roll. Half the fun is having the players work around the trap. Allow non-traditional bypass methods and always always always provide XP for the trap if they get past it - even if it springs and deals damage to them, they disable it, or they circumvent it some way you hand't anticipated.

[Knaight]

The issue with traps often being kind of boring can be circumvented, but that still leaves a number of cases where failed perception checks matter. I generally just provide information regardless - failure just doesn't get you the information you're looking for. In a more humorous campaign, really awful failure gets you information that is downright wrong.

[razorback]

One thing I think works is to come prepared with a spreadsheet/block grid for each player. Either you pregen a bunch of sheets or have them roll and fill in the blocks.
As you require rolls for things like perception, you check off the first block and use that for their roll (works best if you have a copy of their sheet, or, at least, a quick sheet with the pertinent stats/modifiers).
This increases the speed of the game and allows you to give out relevant information as needed without showing your hand by going 'give me a perception check'.
Of course, if they are actively looking, you can either use the sheet or allow them to roll for the check. I would just make sure everyone is on board ahead of time.

[thematgreen]

I've always used a simple method to make my traps and such less predictable. I simply call for a Perception/Knowledge/etc roll, nod, doodle on my side of the GM screen and continue on. I also include extra details randomly that have no threat, but grab interest. Such as "The door seems off center and you can see a line of metal on the hinge side." That's all, but it COULD be a trap, or it could be nothing but extra detail.

By mixing in the harmess with traps and such the group can't predict a trap coming up or other stuff.

It seems to work very well.