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Frozen_Feet
2013-07-24, 02:23 AM
This is a fairly generic system for stealth games, intended to be used with D&D Next, but can be easily adapted to any d20 system.

Stealth missions

Stealth mission refers to any attempt to move in, out or through an area while rousing minimal attention. While combat is not guaranteed to happen on a stealth mission, it shares some key traits with combat scenarios: namely, precise tracking of time, movement and locations of characters. While the operative time unit of stealth missions is usually closer to 1 minute than 1 round (=6 seconds), round-per-round processing of actions may be necessary when moving in close proximity of sentries.

Basics of Stealth

There are four basic states of hiddenness, modified by spells and special abilities. They are:

In Plain Sight: the character is not trying to hide. No check is required to spot him. If he steps within line of sight of any character, that character can notice him.

Sneaking: the character is trying to avoid attention while on the move, using shadows, camouflage or partial cover to mask his presence. Sneaking is usually conducted at just half the normal movement rate. The check DC to sneak is 5 points higher for the same conditions as hiding. Unaware characters do not notice the character.

Hiding: the character is trying to avoid attention by staying still in shadows or partial cover or while using camouflage. Hiding uses basic Stealth check DCs. Unaware characters do not notice the character.

Covered: the character is in total cover and a potential observer can't draw direct line of sight to him. Exact position of the character can't be known, but he can be indirectly detected unless hiding.

To successfully hide or sneak, a character must succeed in a Stealth check against DC based on the conditions he's in. To be able to make a check in the first place, he must be either:


In partial or total cover
Concealed by shadows, darkness, opaque mist, smoke or similar
In a crowd where there are at least 4 people in plain sight adjacent to him
Behind a character who is at least one size category larger
Wearing camouflage


The following conditions preclude making a stealth check:


Being in plain sight to any character you are trying to hide from
Carrying an open light source (such as a torch)
Being completely lit (without wearing camouflage)
Being completely lit and moving (even with camouflage)

The character does not have full knowledge of how well he is hiding or sneaking. He will only know for sure once he faces potential observers. This can be done in the following ways:


The GM tells the DC, but rolls for the character in secret.
The player rolls openly and knows his result, but doesn't get to know the exact DC.
The GM keeps both exact DC and result of the roll as secrets.


A failed check means the character is in plain sight. Once a character is succesfully hidden or sneaking, he will remain that way unless someone makes a succesfull search check to find him, or he is forced into conditions where sneaking and hiding are impossible (namely, bright light with no available cover). This means a succesfull sneak may remain unnoticed by unaware observers almost infinitely.

{table=head]Stealth Conditions | DC
Silenced and Invisible | 0
Silenced and in total cover | 5
Invisible | 5
In total cover | 10
In partial cover with camouflage | 10
Concealed with camouflage | 10
In partial cover | 15
Concealed (by shadow, smoke, mist etc.) | 15
In a crowd | 20
Wearing just camouflage | 20
Behind a larger creature | -5 per difference in size category
Sneaking | +5
Wearing conflicting colours (white against black etc.)* | +5
Wearing reflective items (bare steel etc.)* | +5
Moving at one-quarter speed** | -2
Wearing padded shoes*** | -2
Speaking with a whisper | +2
Speaking with normal voice | +5
[/table]

* Ignore if invisible.
** applies only when sneaking.
*** applies only when sneaking. Ignore this adjustment if silenced.

DC of 0 means the character can always hide succesfully. See "Stealth and special abilities" for further details on invisibility and silence. DC adjustments are cumulative.

Armor check penalty applies to stealth check made to sneak, but not to checks made to hide.

Basics of Observation

There are two basic senses almost all creatures use to spot intruders: sight and hearing. They may also have special sense as shown in their statistics - these will be dealt with later. Sight and hearing have defined ranges, varying from creature to creature. In bright light, sight has practically limitless range, but may be limited by obstacles (such as curvature of a planet). In twilight or darkness, it is sharply limited. The area which a creature can see is called its line of sight. Hearing is more limited, but is not always blocked by same obstacles as light. The area which a creature can listen to is called their hearing range.

In addition to a character's senses, whether it will detect an intruder depends on its state of alertness. There are four basic levels of alertness:

Unaware: the character is not specifically looking for anything, and is reliant on unsorted stimuli their senses pick up routinely. An unaware character will automatically spot characters in plain sight when they fall inside his line of sight, and will automatically hear noises as loud as or louder than normal speech. Unaware characters will not search for sneaking or hiding characters.

Alert: the character is not looking for any specific sneaking or hiding character, but is maintaining a constant vigilance of his surroundings. This is mentally taxing, so a character can only stay alert for a number of minutes equal to his Wisdom score, before his attention lapses and he becomes unaware for 1 minute minimum. An alert character will not search for hidden characters, but is entitled to make a Perception check when a sneaking character first passes through their line of sight or when a sneaking or covered (but not hiding) character first comes within hearing range. In the first case (sight), a succesfull check means the sneaking character's cover is blown, and he is now in plain sight. In the second case, the sneaking or covered character remains hidden, but the alert character becomes aware.

On patrol: as Alert, but the character has standing orders to periodically search certain places. The character will automatically search obvious hiding spots (behind doors, under beds, unlocked rooms), as detailed in his orders, whether anyone is actually hiding them or not.

Aware: this character knows something is amiss and is actively looking for an intruder. He is automatically entitled to a Perception check first time a sneaking or hiding character comes within his line of sight. If the check is succesfull, the intruder is found and is now in plain sight. He is also automatically entitled to Perception check first time a sneaking or hiding character comes within his hearing range. A heard intruder is still hidden, but the aware character can us Perception to approximate the area they're in. As usual, to make a Perception check to find a covered character, the aware character must move so he has line of sight to the intruder. If the initial free checks to spot the sneak fail, the aware character can keep searching but uses the normal searching rules from thereon. If the intruder succesfully slips away from both the aware character's line of sight and hearing range, the aware character will drop to either Alert or On patrol after a number of minutes equal to his wisdom score.

Characters will only move up in categories if they have a reason to. Unaware characters will only become Alert if they expect danger or tense situations. Alert character only become Patrolling characters if given orders by a convincing authority. Alert and Patrolling characters only become Aware if they spot or hear an intruder, if an alarm is sounded, or if they find compelling evidence of intruders being present. Compelling evidence could include (but is not limited to):


dirt or bloody footprints
broken accessories
missing valuables
dead bodies


Basics of Spotting and Searching

Spotting and Searching use the Perception skill. As detailed above, only Alert, Aware and patrolling characters are entitled to make the checks for spotting. Spotting uses the same DCs as searching. Searching is a more deliberate, time-consuming effort. Every 5' square takes 1 round (=6 seconds) to search if the DC to find a hidden character or object is 15 or less, and 1 minute if the DC is above that. Just like an intruder doesn't know how stealthy he is, searchers and spotters do not know how well exactly they have looked. Multiple attempts are of course possible, but cost time.

{table=head] Pereception Conditions (sight) | DC
Target is lit and moving | -
Target is lit but in a light crowd + | 0
Target is lit but in a moderate crowd + | 5
Target is lit but in a thick crowd + | 10
Target is lit but wearing camouflage* | 5
The target is hiding in light shadows, smoke or mist | 10
The target is hiding in heavy shadows (night), smoke or mist | 15
The target is hiding in pitch-blackness (enclosed room) | 20
The target is wearing camouflage* | +5
The target is in partial or total cover** | +5
The target is in a crowd of larger people | +5 per difference in size category
The target is sneaking | -5
The target is invisible | +10
The target is bleeding, dripping wet, covered in chalk etc. | -5
The target is on an easily imprinted surface (snow etc.) | -5
The target is wearing conflicting colours (white against black etc.)* | -5
The target is wearing reflective surfaces (bare steel etc.)* | -5
Character is moving with a crowd ++ | +5
Character is moving against a crowd ++ | -5
[/table]

+ in a light crow there are 1 to 10 people between the observer and the target. In a moderate crowd, there are 11 to 25 people between them. In a thick crowd, there are 26+.
++ don't apply normal modifier for sneaking target
* ignore if the target is invisible
** targets in total cover are not eligible for being spotted outright. Targets in total cover must be searched for in a time-consuming manner.

{table=head]Perception Conditions (hearing) | DC
Target is moving on a rough surface (loose gravel, creaky floorboards etc.) | 5
Target is moving on a hard surface | 10
Target is moving on a soft surface (heavy mattress etc.) | 15
Target is still | 20
Target is still and in total cover | 25
Target is still and in a sound-proof container | 30
Target is wearing padded shoes | +2
Target is whispering | -2
Target is speaking in a normal voice | -5
Target is shouting or casting a spell | -10
Target is silenced | +10
[/table]

DC of - means the target is in plain sight. Even unaware characters notice him with no check.

DC of 0 means unaware characters keep ignoring the target, but alert, aware and patrolling characters automatically spot him. Unaware characters only need someone to point out the presence of the target to notice him.

If the perception check is succesful and the hiding/sneaking character is within line of sight of the observer, the sneak's cover is blown and he is now in plain sight. If the sneak is not in line of sight, but is withing hearing range, the sneak remains hidden but the observer can now make additional search checks to find him. First succesful perception check to hear a hiding/sneaking target will reveal which 10' by 10' area they're in, or which direction they are moving towards. A second succesful perception check to hear a hiding/sneaking character will reveal which 5' by 5' square they're in.

Frozen_Feet
2013-08-03, 09:03 AM
DCs for various situations have been added. I will next work on sample scenarios to show how this system is supposed to work in practice. Questions and comments are welcome and will hopefully be answered in the examples.

DMMike
2013-08-03, 11:48 AM
Comprehensive. I'd put this on my GM screen if I were a tables sort of guy.

You might want to add some rules for distance, though. The eyes notice larger things before they notice smaller things.

Frozen_Feet
2013-08-04, 02:09 AM
Rules for distance (and special senses) are forthcoming.

---

Example Scenario 1:

Rudolf the Robber is on the run from coppers. Between him and his hideout, however, is a busy marketplace. Rudolf starts to sneak in dark alley, out of the townsfolk's view. He rolls 16 against the DC of 15, and so the unaware townsfolk will not mind him as he wades through the crowd. However, if any of the alert coppers reach the marketplace before Rudolf reaches safety, they can spot and point him out, in which case the whole market knows there's a thief amongst them! But if the coppers are late and start to ask questions, they will be none the wiser as none of them paid attention to Rudolf even though he was just there!

Notes: Rudolf improves his chances to be unnoticed by 50% by starting his stealth well-beforehand in good conditions. Slipping into a crowd from the shadows is much better than attempting a vanishing trick in the middle of it. To increase his chances to avoid the coppers, Rudolf could have a larger henchman to help him hide, and he could hug the shadowy edges of the marketplace.

qazzquimby
2013-08-04, 08:14 PM
I don't think this is getting enough attention. It's too rules heavy for just some casual sneaking, but I will definitely be using this whenever stealth is important to the adventure. It reminds me of Mark of the Ninja with the way hearing works as well as the statuses like alert and aware.
Thanks for making this.

Frozen_Feet
2013-08-05, 04:08 AM
If by "casual sneaking" you mean a situation where only or mostly unaware observers are to be expected, these rules should be less roll-intensive than normal rules for stealth. Just make a roll to hide, and if succesful, people will ignore you.

Most of these rules are indeed made for a situation that can't be called "casual" in the slightest - a serious investigation, infiltration or escape attempt, where you can expect to be looking for something, or for someone else to be looking for you.

Jormengand
2013-08-05, 11:41 AM
This is mentally taxing, so a character can only stay alert for a number of minutes equal to his Wisdom score, before his attention lapses and he becomes unaware for 1 minute minimum.

So the average city guard is incapable of ever being alert, and a paragonal character can only stay alert for five? This seems odd.

Cicciograna
2013-08-05, 11:55 AM
So the average city guard is incapable of ever being alert, and a paragonal character can only stay alert for five? This seems odd.

Wisdom score, not bonus.
So the average city guard can be alert for about 10-11 minutes, and the paragonal character even for 20+.

Jormengand
2013-08-05, 12:12 PM
Wisdom score, not bonus.
So the average city guard can be alert for about 10-11 minutes, and the paragonal character even for 20+.

Oh, right. Duh. *Hits head against wall.*

Hanuman
2013-08-05, 03:06 PM
This would be great for a big heist, or something that puts on its gum boots and really wades into the realms of stealth.

Otherwise, it would actually be more helpful to write an actual guide on stealth, and how to balance it in a modular way.

For instance, you could cover one thing with a flavor sentence then add you should probably add another +2 or -2 for the DC of it, that sort of thing would educate DM's, who are the ones who will be handling 99% of all the stealth mechanics anyway.

Frozen_Feet
2013-08-07, 07:56 AM
For instance, you could cover one thing with a flavor sentence then add you should probably add another +2 or -2 for the DC of it, that sort of thing would educate DM's, who are the ones who will be handling 99% of all the stealth mechanics anyway.

Uh, that is precisely what all those tables are. Besides, I prefer actual rules to guidelines. :smalltongue:

I may write a bit free-er guide for using these rules and adjucating stealth scenarios in general in the future, mainly to divulge why this system is as it is.

Morgarion
2013-08-07, 11:37 AM
If I'm reading this correctly, there seems to be a problem with the mechanism for hiding in the crowd, at least. Assuming two characters with no modifiers or ranks or anything, I can hide in a crowd with a roll of 20 - but that doesn't do me any good because you can never not find me.

Maybe I missed something, but I also don't see the modifiers taken into account for setting difficulties of the other person's checks. So, even though I might be really good at hiding (high Dex modifier, several ranks), the DC to spot me is the same as someone who, all else being equal (circumstances), has no ranks and a lower Dexterity score.

I don't mean to rain on your parade, but intuitively this doesn't feel balanced to me.

Frozen_Feet
2013-08-08, 12:40 AM
If I'm reading this correctly, there seems to be a problem with the mechanism for hiding in the crowd, at least. Assuming two characters with no modifiers or ranks or anything, I can hide in a crowd with a roll of 20 - but that doesn't do me any good because you can never not find me.

The check DC to find a lit character in a crowd is "0", not "-". Unaware characters do not automatically get a check, even if they would always succeed.

So if the person you're trying to hide from is unaware, you only roll for hiding. If succesful, the unaware character will ignore you unless given a good reason to look for you.


Maybe I missed something, but I also don't see the modifiers taken into account for setting difficulties of the other person's checks. So, even though I might be really good at hiding (high Dex modifier, several ranks), the DC to spot me is the same as someone who, all else being equal (circumstances), has no ranks and a lower Dexterity score.

I don't mean to rain on your parade, but intuitively this doesn't feel balanced to me.

First, Dex and Hiding skill are already taken into account when you make the initial Stealth check. Having them also impact Search DCs would mean counting them a second time - that is what's not balanced or fair.

Second, if skill of the sneak was checked a second time, this would mean skill of the perceiver would also have to be accounted for in the stealth check. But this is both needlessly complicated, and also equal to going back to opposed rolls. There is a very good reason these rules do away with those. I will explain them in the forecoming guide, but in the interim, see the 5th edition discussion thread for all the problems opposed rolls have in a system with bounded accuracy.

Morgarion
2013-08-08, 07:53 AM
The check DC to find a lit character in a crowd is "0", not "-". Unaware characters do not automatically get a check, even if they would always succeed.

Aware, alert, whatever. My point was just that the system allows for this situation where one can successfully hide, but that success is meaningless because people looking for them will always succeed. And this one might very well be a minor and irrelevant footnote, depending on whether crowds offer concealment or if you can move while hiding without attempting to sneak.


First, Dex and Hiding skill are already taken into account when you make the initial Stealth check. Having them also impact Search DCs would mean counting them a second time - that is what's not balanced or fair.

Second, if skill of the sneak was checked a second time, this would mean skill of the perceiver would also have to be accounted for in the stealth check. But this is both needlessly complicated, and also equal to going back to opposed rolls. There is a very good reason these rules do away with those. I will explain them in the forecoming guide, but in the interim, see the 5th edition discussion thread for all the problems opposed rolls have in a system with bounded accuracy.

I don't know where this 'second time' stuff is coming from; the hider's ranks and modifiers, along with the roll and the adjustments for circumstances constitute the search DC. One roll for the hider, one roll for the searcher with a DC based on the hider.

I see that the Dex and Stealth affect the success of the hider in the first place. But what I don't understand is why when all else is equal, a character with extensive training in stealth and high dexterity is just as easy to spot as a character with no ranks and no dexterity modifier.

I am familiar with what this is supposed to represent and I am aware that the first character will have an easier time achieving a state of being hidden. What, in my opinion and according to my own tastes, seems to be missing is a way to represent the first character achieving a better state of being hidden.

Thanks for giving me the opportunity to clarify my points.

Frozen_Feet
2013-08-08, 08:43 AM
Aware, alert, whatever. My point was just that the system allows for this situation where one can successfully hide, but that success is meaningless because people looking for them will always succeed.

The point is to allow hiding from or sneaking past people who are not looking for them. In this system, unaware is the default, assumed state. Anything above that requires specific effort on part of the searcher.

For example, a crowd at a market place, or a bunch of drunken party-goers.

Morgarion
2013-08-08, 09:31 AM
I understand that. I guess we just have different intuitions about how hard it should be for someone who is actively looking for someone else to find them in a crowd. Or maybe we have different intuitions about what constitutes a crowd.

I would have expected for Rudolf the Robber to be able to slip into a crowd to get away from the guards to be a more effective strategy. As you have it, I am left with the impression that Rudolf enters the crowd and hides, remaining unnoticed by the people in the crowd itself. Then the guards arrive and scan the area and when their line of site passes over his position, they see him. As long as they don't have any negative modifiers, Rudolf gets noticed by them. The DC to spot a character hiding in a crowd is 0 - no bonus for the concealment granted by all the people, no chance of disappearing into the bustle. Right?

Frozen_Feet
2013-08-08, 09:42 AM
Some modifiers depending on the heaviness of crowd will be in place, then.