How do I run stealth and perception? Passive perception vs active perception

Question

I'm a new dm and I want to introduce some ambush style encounters in my game. I told my players recently that I will not ask them if they want to be steathly when moving around a dungeon because I feel like I'm tipping them off about potential danger. In addition I told them when it comes to things like noticing traps or monsters I will use their passive perception unless they say they want to look for these things.

My concern is that by doing this, I have created an environment where my players are constantly opening doors and implying they want to make perception checks. It bogs the game down, and I find it hard to set any trap or ambush when I have 5 players spamming these checks. Chances are someone will roll high enough to see something. If I just use everyone's passive and tell them they can't just keep making active perception checks I feel like I'm doing something wrong, but it also feels bad to allow every single player their passive attempt and active attempt to notice danger. How do I run this in a way thats efficient and fair, but also presents a level of danger for players who are "too careful"?

If a player opens a door and I describe what they see and they ask "do I see any monsters?", do I tell them no if their passive score wasn't enough and let them walk into the ambush, or do I give them an active perception roll? On one hand if I dont give them the roll if feels like I cheated them out of a chance to notice the threat. On the other hand if I do give them the roll then it feels like whats the point of even having passive perception if my players are just going to throw dice everytime they open a door anyways and basically getting 10 chances as a party to notice danger.

If I only allow 1 player to roll a perception check my players will wait to see his result and if he rolls low enough the other players just take turns making checks until someone passes or they all fail. This seems like something that shouldn't happen, but I also don't know how to stop this from happening.

Answer 1

You decide when they get to make a check, but if they are actively looking, they should

The DMG has this guidance on when to ask for checks (p. 237):

When a player wants to do something, it's often appropriate to let the attempt succeed without a roll or a reference to the character's ability scores. For example, a character doesn't normally need to make a Dexterity check to walk across an empty room or a Charisma check to order a mug of ale. Only call for a roll if there is a meaningful consequence for failure.
When deciding whether to use a roll, ask yourself two questions:

• Is a task so easy and so free of conflict and stress that there should be no chance of failure?
• Is a task so inappropriate or impossible-such as hitting the moon with an arrow-that it can't work?

If the answer to both of these questions is no, some kind of roll is appropriate.

This is the situation you have: the players are having their characters look around for hidden traps or enemies, actively, by declaring they do so. They have a chance to succeed or fail, and the outcome has consequences. This is the classic situation for an active perception check.

When the opponents cannot be seen from the player's position, and player that says they are checking for hidden foes, you need to determine if they have any chance to detect something. Vision is not all, odor, breath, noises, tracks all can be revealing. If you determine it's impossible, there is no check neither active nor passive.

The rules technically allow you to use passive checks there. It is one of the examples for when to use them:

when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.

The motivation here however is on secretly. You don't want to roll dice behind the screen, so the players who are blissfully unaware of a possible trap are not getting suspicious of what is going on. Not, because you want to cram a "surprise" ambush down their throat, that everyone is expecting.

I can tell you there is little that feels as grossly unfair to players as when they do everything they can to see if there is an ambush because they suspect one, and then you just go and spring one on them and have them suffer surprise — just so you can run your ambush and because the rules allow you to. This is zero fun.

When the DMG rules for surprise say

The DM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn't notice a threat is surprised at the start of the encounter

it refers to the surprise rules in the PHB, page 182, to activities under the heading "Activity while traveling", so the context is one of longer activity, not one of concentrated action like when you open a door, ready for an ambush and say you are looking for one.

How to avoid tiresome constant checking

If this behavior leads to repetitive play, one way to help is to just tell them there is nothing found from time to time without rolls (not always or they'll quickly figure out that something is there whenever you ask for a check, leading to the classic "wait! I just failed a spot check" trope).

What also can help is to not use that many traps or hidden enemies. Most groups tend to ease up after some time. Traps should be sparse, if you put one in every room, people of course will check all the time.

But, if you have a group that is obsessive about it, with checklists and SOPs, they may not forget. In that case, it might be best to have a discussion with them about how they want to play off-table, and find out if they are happy doing this. If they are, let them do it. Another option to speed things up is to pre-roll sets of these checks for them, and they can use standing orders of them doing this, you just tell them what they saw.

Because passive checks have no variance, they may be unable to catch a higher-DC trap, where you still have a small chance with active checks, and more so with a larger group. You can explain that you'll use passive checks to speed up play if they do this all the time but it is giving them a slight disadvantage, and so maybe is not entirely fair.

Answer 2

RAW, active and passive describe the rolls, not the characters

First off, let's deal with a common misconception. Active Perception is not when a character 'actively looks' for hidden monsters, it is when the player actively makes a Perception roll. Passive Perception is not an intuitive sense the characters have even when they don't search, it is when the DM determines a result by using the passive Perception score of a character without the player making a roll. Thus, 'active' and 'passive' refer to what the player and DM are doing in the meta-game, not what the characters are doing within the narrative, and you should not be determining whether the players 'get' an active roll based on what they say their characters are doing, but rather on how you as a DM want the meta-game to proceed.

The purpose of passive checks is explained in the PHB (emphasis mine):

A passive check is a special kind of ability check that doesn't involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster

If your players have a dedicated scout, and both you and they are comfortable with that character's player making active Perception checks (that is, rolls) upon entering a new area but not metagaming the results, active checks are perfectly appropriate. That is, a scout doesn't know whether she is not seeing monsters because there are no monsters, or whether there are monsters there but they are very well hidden, or whether there are monsters there and they are hidden poorly but she looked for them even more poorly. The characters know the result of an action, they don't know the result of a player's roll. If your players are capable of seeing a poor roll and having their characters walk into the room trusting that it has been scouted (despite their own meta-knowledge as players), then go ahead and call for the roll. But if your players exhibit the behavior you described - the scout rolled low so suddenly everyone wants to make a check - then as a DM you are well-advised to switch to passive checks. Your players have shown that they can't be trusted with meta-information about how 'good' a roll was, so you simply don't give them that information. By definition, passive checks are used "when the DM wants to secretly determine whether the characters succeed at something without rolling dice."

A second misconception is that passive perception is 'always on', that it is an intuitive sense that represents the absolute worst awareness a character could have in any situation. In fact, the rules assume that a character is always actively looking for danger (the character is active, even when the check is passive) - otherwise they would not have survived this long in a violent and dangerous profession. Even though a character is always actively looking for danger, they do have limits - limited attention and limited time. Passive perception checks should not be allowed when a character is busily engaged in something else. As the PHB explains about Noticing Threats (emphases in the original):

Noticing Threats Use the passive Wisdom (Perception) scores of the characters to determine whether anyone in the group notices a hidden threat. The DM might decide that a threat can be noticed only by characters in a particular rank. For example, as the characters are exploring a maze of tunnels, the DM might decide that only those characters in the back rank have a chance to hear or spot a stealthy creature following the group, while characters in the front and middle ranks cannot...

Other Activities Characters who turn their attention to other tasks as the group travels are not focused on watching for danger. These characters don’t contribute their passive Wisdom (Perception) scores to the group’s chance of noticing hidden threats. However, a character not watching for danger can do one of the following activities instead, or some other activity with the DM’s permission...[Navigate], [Draw a Map], [Track], [Forage].

Thus, when you are using passive Perception, characters will automatically notice threats based on their scores - so long as they are in a physical position that allows them to actually perceive the threat and only so long that they are not engaged in another task that requires all of their attention.

In your case, you have a group of meta-gaming players who open a door and ask if they can see any monsters in the room. RAW, you compare the Stealth scores of Hidden monsters to the passive Perceptions of any of the characters who can physically see into the room in their current position and who aren't otherwise engaged in any attention-demanding tasks, and then you report the results. No dice are rolled.

What style of game do you want?

You have told us that you "want to introduce some ambush style encounters in" your game, but that you are concerned you have "created an environment where [your] players are constantly opening doors and implying they want to make perception checks. It bogs the game down" and ultimately with enough players the ambush will be perceived anyway. Further, you want a procedure that is "efficient and fair, but also presents a level of danger for players who are "too careful"".

You can do all this with passive checks. First, you need to establish that the scout can spot most creatures attempting an ambush. Make sure you have a few encounters that are failed ambushes - challenging in their own right, but which could have turned real bad if the scout hadn't spotted the hidden foes and tipped the players off. Choose creatures whose passive Stealth is lower than the party scout's passive Perception, and in your narrative description emphasize that it is only because their designated scout is especially perceptive that the ambush was averted - they enemy was trying to Hide, the rest of the party would have missed the Hidden foes, but the scout was able to see the enemy and alert the party. After a few of these encounters, the party will learn that they can trust their scout's passive Perception to keep them aware of Hidden threats.

Once they have internalized this message, then you throw them a curve - Hidden monsters whose passive Stealth is above the scout's passive Perception, such that there is no way they could know about the ambush. Make sure the monster(s) are such that without surprise, it would have been an easy fight, but the encounter is challenging because the ambush worked. If it was a challenging encounter to begin with and then you added 'automatic surprise' on top of that, the players would likely feel like you had become an unfair, adversarial DM.

Now the players know something else - their scout is usually up to the task of spotting Hidden foes, but some monsters are just too good at hiding.

How they react to that is up to them, and it could change the play style of the game. It might make them "too careful", but that is fine if they enjoy this style. Many old school D&D games were about resource management, cautious exploration, and opportunistic looting - combat was avoided if at all possible. The 'danger of being too careful' here is twofold - the risk of boredom if your players are more interested in action than exploring, and the opportunity cost of spending in-game time being careful if they do welcome that kind of play. Time is also a resource they can run out of.

If you don't think this style is for your group (and you should have a meta-discussion if in doubt), reassure them that the kinds of monsters that rely on their superior, undetectable ambushes are rare. There is always a chance of them, increasing the tension of exploration, but they are actually rare, such that it is usually more worthwhile to simply trust in the passive Perception of the scout. Those are the kinds of interesting decisions the players should be making, risk vs. reward comparisons that rely on them investing in an understanding of how your world works.

Answer 3

Consider using DMing technics

Your job as a DM is to facilitate engaging and fun gaming experience. Following the game rules doesn't do this automatically. The rules only provide a solid toolset for us DMs to use. In addition to it, good DMs also borrow various writing ideas or game design technics to ensure an enjoyable game.

In order to do that, try to reduce your dependance on dice rolls. Throwing dice might be fun, but it also makes the game more chaotic, can cripple the narrative with unimportant details, which leads to bad (not fun) game habits.

Your players seem to treat dice rolls as a resource:

"if I dont give them the roll if feels like I cheated them"

"they want to make perception checks"

However, it's quite the opposite in the rules: out of combat, dice rolls are meant to be made only "when the outcome is uncertain". The DMG explicitly allows running the game without dice at all:

One approach is to use dice as rarely as possible. Some DMs use them only during combat, and determine success or failure as they like in other situations.

It's important to mention, that the role of dice was being changed through editions. Actually, 5e doesn't have skill checks anymore, although "I use my X skill" approach is still very popular.

Without asking for a Wisdom (Perception) check, there is still plenty of options you can choose from:

• Cut straight to the action
• Skip unimportant details
• Engage players in problem-solving activities
• Ask questions and describe the outcome

Cut straight to the action

— Do I see any monsters?
— You do, actually. There are four hobgoblins crouching behind a long, overturned table. They see you too, one of them is rasing his crossbow, and the second one is starting to blow an alarm horn. Roll for initiative!

It is still very "ambush style", despite the fact that no one was surprised. The party is caught in cramped corridors, and reinforcements are coming.

Skip unimportant details

— Do I see any monsters?
— Nope.

Of course, the room should be empty. Be honest with your players.

Engage players in problem-solving activities

— Do I see any monsters?
— Not yet. However, this particular room looks suspiciously cluttered. There is a long, overturned table in the middle of it, which looks like a convenient place to hide. What do you do?

It's possible nobody was hiding behind the table, but the players should reveal this with their actions, not just dice rolls.

— Do I see any monsters?
— No you don't, but you can't see the whole room from this angle. It also has no windows, so it's especially dark there. What do you do?

"How do you do that" is also a powerfull question to derail players from the "I use my Perception skill" mindset. When a controversial situation emerges, be on the players' side — always assume reasonable behavior, don't play "gotcha!" with them.

Without unnecessary dice rolls, players will stop spamming with ability checks. The game will be faster and (presumably) more fun.

Answer 4

here is an alternative If you want to bypass the whole "player's searching for hidden dangers" thing and still run an ambush scenario, flip it on its head. The monsters get the drop on the players because the PCs aren't being stealthy. This could be as simple as kerrek the kobold readying an action to throw his tanglefoot bag at whomever is trying to break down his door. It could also be as elaborate as a treasure room with a bunch of sealed pots that players are likely to break open, alerting the hobgoblins in the next room, who surround the room and kick in the doors, guns (crossbows) blazing. By placing the enemies in a position they are unlikely to be detected, they can avoid the perception check problem, and you get the added vindication that the players contributed to their character's plight by alerting the enemy.

Answer 5

The first conversation that needs to happen (and it sounds like you have some of it handled) is to talk consent with the party and see where the edges of their comfort zone are. When they make their characters, that's sort of it unless they want to start all the way over. You as the DM can literally invent things after those stats are solidified that they have no chance of beating, and that's where it hits a wall.

I once asked a question, "Is it OK to sic assassins on my PCs" in the same vein. At what point is it unfair to bring these types of things against the players? The answer to that question was to warn the players both subtly and overtly.

• Tell them that there are some tough threats of this variety
• Ask them how they feel about events beyond their control
• The more dangerous the threat in question, check that they have a way to plan around it. For example, it only takes one bandit ambush during a long rest to teach a party to set up watches. Have them meet a ranger who warns them about 'the dangers of these here parts'.
• If the party is being passive, use passive. If the party is being active, use active.
• Combining a couple of points, if it's going to be tough, maybe roll for the characters in question while planning and see if it beats their passive. This goes hand in hand with consent from the players so they don't feel railroaded.
• Just as you can create the indomitable, don't be afraid to have a plot device standing by to save the party if things go worse than you expected. (For example, a DM I had didn't read a monster ability close enough and it resulted in a one shot kill of a PC - that monster just so happened to drop a potion of revivify in addition to the planned loot and the DM apologized)
• Scale the challenges, ask yourself what the "fun" part of this is going to be. You wouldn't use an ancient dragon just because you want something that can survive the first round of combat.