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Example: A fighter is concerned by the potential of ambush and scans the suspected area. For certain, there are goblins hiding in the thicket he suspects.

Should the DM have the fighter roll a Wisdom (Perception) check? If so, what would that be compared against?

I see two possible ways to resolve this:

  1. Compare the fighter's roll against a Difficulty Class number that the DM deems appropriate, or
  2. Compare the fighter's Perception roll to a Stealth roll made for the goblins (if this were the case, would the DM roll once for the entire group of goblins?). But this then would seem to be a contest?
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The PC makes a Wisdom (Perception) check, contested by each hidden enemy's earlier Dexterity (Stealth) check

The rules for hiding are given in the "Hiding" sidebar by the descriptions of Dexterity checks (here in the basic rules, or on PHB p. 177):

The DM decides when circumstances are appropriate for hiding. When you try to hide, make a Dexterity (Stealth) check. Until you are discovered or you stop hiding, that check's total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence.

You can't hide from a creature that can see you clearly, and you give away your position if you make noise, such as shouting a warning or knocking over a vase. An invisible creature can always try to hide. Signs of its passage might still be noticed, and it does have to stay quiet.

In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the DM might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack roll before you are seen.

Passive Perception. When you hide, there's a chance someone will notice you even if they aren't searching. To determine whether such a creature notices you, the DM compares your Dexterity (Stealth) check with that creature's passive Wisdom (Perception) score, which equals 10 + the creature's Wisdom modifier, as well as any other bonuses or penalties. If the creature has advantage, add 5. For disadvantage, subtract 5. For example, if a 1st-level character (with a proficiency bonus of +2) has a Wisdom of 15 (a +2 modifier) and proficiency in Perception, he or she has a passive Wisdom (Perception) of 14.

What Can You See? One of the main factors in determining whether you can find a hidden creature or object is how well you can see in an area, which might be lightly or heavily obscured, as explained in chapter 8.

The description of the Hide action reiterates that you make a Stealth check to do so, as described in the "Hiding" sidebar. It also references the benefits of hiding as given in the "Unseen Attackers and Targets" section of the rules; if you make an attack from hiding, you have advantage on the attack, and become unhidden right after the attack.

In short: a creature that tries to hide makes a Stealth check. If other creatures are not actively searching for it, that Stealth check is contested by other creatures' passive Perception.

If other creatures are actively looking for the hidden creature, they can take the Search action:

When you take the Search action, you devote your attention to finding something. Depending on the nature of your search, the DM might have you make a Wisdom (Perception) check or an Intelligence (Investigation) check.

In this case, since the player character is looking for a creature and not trying to locate a secret door, the PC makes a Perception check contested by the hiding creature's previous Stealth check made when it tried to hide.


To save time, you could make a single check for the entire group of enemies. It would work the same way, except you're just making a single Stealth check for the enemies. That Stealth check is still contested by the searching creature's Perception check. If the Perception check beats the Stealth check, all the hidden enemies are discovered.

(An alternative suggested by some others is to avoid making an active Stealth check roll altogether, and simply treat it as a passive check by contesting the Perception check with a passive value of [10 + the goblins' Stealth modifier]. Personally, I'm not a huge fan of this, as it means that unless the players think to look for the enemy, you're simply automatically deciding that the players either will or won't be surprised by comparing two static numbers to one another. When there's no rolling at all by either group, where's the fun in that?)

This isn't necessarily governed by a specific rule; it's just a time-saving measure. Note that you'd only do this if all the enemies were the same type of creature, and thus had the same Stealth modifier. If there are multiple different types of enemies, you should make separate checks for each kind of monster.

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    \$\begingroup\$ The paragraph "To save time..." might be improved by suggesting the possibility of using Passive Stealth to get an effective average rather than making a single swingy check for an entire group. \$\endgroup\$ – Bloodcinder Feb 10 at 3:35
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DM rolls for goblins and has passive perceptions written down unless the players explicitly state that they're on the lookout for ambushes.

If he's specifically looking I would have it be a set DC as a kind of passive stealth. 10+Goblin Stealth bonus. One fixed value for the whole group.

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  • \$\begingroup\$ Welcome to RPG.SE! Take the tour if you haven't already, and check out the help center for more guidance. Could you explain why you'd use a set DC of 10+goblins' Stealth mod if the PC is actively looking? How do the PC's actions relate to what number you use for the goblins' Stealth? \$\endgroup\$ – V2Blast Feb 10 at 1:25
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    \$\begingroup\$ You can improve this answer a bit in the following ways. First of all, always cite specific rules when you are able, your first paragraph makes mention of passive perceptions and how they relate to detecting an ambush, cite the page in the appropriate rulebook to help the querent identify where to look. Second, your second paragraph discusses active searches and group detection, again cite the relevant rules, I think there's a good section on that in the DMG, which the querent would benefit from. \$\endgroup\$ – Pyrotechnical Feb 10 at 2:10
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    \$\begingroup\$ Third, expand your answer to be more than a declarative statement. There are some vagaries in the question, ensure that any assumptions you are making are clearly stated; for example, you've addressed passive detection, but it doesn't appear that the querent's asking about that, I think he's just asking about active checks. Fourth, headers are great! Especially when you're not completely sure that you understand the question, and want to provide an answer that covers all bases as I think this one does; toss in a couple headers for your sections and it'll make it easier to understand. \$\endgroup\$ – Pyrotechnical Feb 10 at 2:13

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