RAI: Nondetection

[FrancisBean]

How do you handle Nondetection in your games? RAW, the spell is a bit of a mess.



For the duration, you hide a target that you touch from divination magic. The target can be a willing creature or a place or an object no larger than 10 feet in any dimension. The target can't be targeted by any divination magic or perceived through magical scrying sensors.

RAW analysis

I'm only getting into RAW analysis to show why I don't think we should simply take the spell as written. I'm not interested in a lot of nit-picky parsing, I just want a functional table interpretation. I know this thread is going to devolve into some RAW argument, but please, let's try to keep that to a minimum, folks. It's only germane insofar that it proves that there are clear, reasonable disagreements, and that's what leads to arguments at table.

In most descriptions, the first part is fluff while the follow-on is actual mechanics. That is, it’s saying that the spell hides a target from divination magic, and it does this by making it impossible to target you or perceive you through scrying sensors.(*)

The scrying aspect is perfectly clear, although it does provide a way to determine if somebody is under the effects of Nondetection: if you can see them with your eyes but not with Clairvoyance, they’re under Nondetection. It’s also a bit of a giveaway when you see someone else holding a conversation with empty air.

The bigger problem is the non-targetability. By far the vast majority of divination spells target the caster or a willing creature, and expand the senses of the target in some way. Not being an eligible target for divination magic means your friends can’t cast Guidance on you. You can’t cast Commune. You can’t partake in Rary’s Telepathic Bond. It’s actually an enormous penalty, not a benefit.

And to make it worse, the things you’d want to use it for aren’t affected by targetting. Detect Evil and Good is a Self spell, allowing you to sense various creature types. A Lich in disguise under Nondetection isn’t the target, so Nondetection doesn’t help. Ditto Locate Creature, See Invisibility, or True Seeing.

It also brings in the complications from Xanathar’s on spell targetability, pg 85-86.

(*)Some of you are going to say I’m misinterpreting that first line as fluff, and that it's actually mechanics. That’s fine, because I’m not interested in arguing over the RAW. I’m trying to figure out a good table interpretation, one which fits that first line without being a mess everywhere else.

But even if we take the first sentence as mechanics, we still have problems. E.g., True Seeing on our Lich under Nondetection would see a blank space! And if we’re being consistent, Legend Lore should be unable to reveal anything about something under Nondetection. A similar argument could be made about Foresight – if you’re hidden from divination magic, you’re hidden from Foresight’s short-term ability to see the future, and someone under it shouldn’t get the mechanical benefits against you.

The interaction of Nondetection, Invisibility, and See Invisibility is particularly likely to lead to table arguments. A player using Invisibility and Nondetection could expect to pass unnoticed through See Invisibility. A player using See Invisibility is going to be similarly upset when an invisible assassin suddenly appears because they just attacked with surprise.

tl;dr: How do you handle Nondetection in your own games?

Here’s where I’m leaning. You can still choose to be affected by Self and Touch spells cast directly on you. Being “hidden” from divination for location/detection spells means you just don’t register as what it locates or detects. For See Invisibility and True Seeing, the spells show a vague, blurred empty space with Disadvantage on Perception. You can't see any details about an undetectable, invisible creature, but you have a chance to notice that something's there. For something like our Lich in disguise, Legend Lore would still work to give details about the Lich from the time periods when Nondetection wasn’t active, but wouldn’t help at all with periods under Nondetection. Scrying sensors don’t “see” you, but they see the vague blur as with See Invisibility, so the scryer knows there’s something they can’t make out. Foresight is 9th level, so I'm inclined to ignore consistency and just say it wins by raw power.

[MaxWilson]

I run it by RAW (e.g. it doesn't prevent See Invisibility from working) and just accept that it's niche. It prevents scrying and is useful to prevent Mind Flayer Elder Brains from pinpointing you, if you're going into Mind Flayer territory.

For anything else you'll have to research a custom spell, which I have rules for and encourage players to do.

[RSP]

“ For the Duration, you hide a target that you touch from Divination magic. The target can be a willing creature or a place or an object no larger than 10 feet in any dimension. The target can't be targeted by any Divination magic or perceived through magical Scrying sensors.”

Not sure why it matters if the first sentence is fluff or not, as it’s effectively the same as the first part of the third sentence anyway.

I take it at what it says: the target of non-Detection cannot be targeted by Divination magic or scryied upon. This is where the whole “spells can have more than one target” thing comes up. A Self spell can also target other creatures if it’s description says it does: (from PHB) “A spell’s description tells you whether the spell targets creatures, objects, or a point of origin for an area of effect.” So having See Invisibility up on yourself, doesn’t mean it’s not also targeting other creatures with it’s described effect (seeing things that are invisible). If an invisible creature also has Nondetection on them, well then they can’t be a target of the See Invisibility spell effect, and so won’t be seen even if the would be perceived has See Invisibility up.

[Segev]

I'd just like to note that that first sentence doesn't read like fluff.

Further, if it's "just fluff," that means...it doesn't require you to touch your target, since that is "fluff?"

It seems to me that ignoring the first sentence, especially in 5e, where rulings and not rules are the directive, is not parsing the RAW, but rather editing the RAW to try to justify a twisted reading that is against the RAW and likely RAI.

Not saying you're doing this, mind; I get that you want a more "clean" interpretation. But the clean interpretation would be to take the first sentence as controlling. If it's a divination spell, it can't detect the protected target. The rest is further detail, but it doesn't override the first sentence. "Birds are not allowed in here. Eagles may be hurt by the close confines," does not say that only eagles are forbidden entry to wherever "here" is.

[Thunderous Mojo]

For me personally if something was both Invisible and subject to the Nondetection spell, then See Invisibility isn't going to see it/them.

I don't see why the interaction would lead to extreme consternation, though, even if the DM handles it differently than how one expected the situation to be handled.

If I was playing in a game ran by MaxWilson, for example, I imagine this situation might come up as a "session zero" topic. Even if it didn't, in the case of Max...Max would give his ruling and explain that while the tactic didn't work as I, (the player), expected...I could make it work ...if I expend some resources later.

That is an eminently satisfactory answer.

As a player,(and as a DM), one has to be prepared that sometimes, (and sometimes quite often), opposing creatures can counter one's moves.

[Unoriginal]

There is no such thing as "fluff" in 5e spell description. What happens is what is described to happen.

[MaxWilson]

I've been thinking about this more, and especially thinking about the wording of the Sequester spell (which is identical). I'm on the verge of ruling that Sequester and Nondetection are badly written, and maybe SHOULD protect against See Invisibility, because otherwise the very expensive Sequester spell loses most part of its value.

I'll have to think about it more, and it might only be Sequester that I rewrite (not that anyone has ever cast it at the table, yet), but it might be both.

[Thunderous Mojo]

I've been thinking about this more, and especially thinking about the wording of the Sequester spell (which is identical). I'm on the verge of ruling that Sequester and Nondetection are badly written, and maybe SHOULD protect against See Invisibility, because otherwise the very expensive Sequester spell loses most part of its value.

I'll have to think about it more, and it might only be Sequester that I rewrite (not that anyone has ever cast it at the table, yet), but it might be both.

I agree that both spells are badly written in 5e.
(Side note going off memory here)...in AD&D Non Detection was clearly stated to only work against Scrying Sensors. The Sequester spell explicitly stated that it rendered the subject invisible to sight and spells.

For 5e I went with the path of least resistance vis a vis Nondetection.
Boosting the Nondetection spell, compared to it's historical antecedents was worth it for me, to avoid arguments or ruffled feathers at the gaming table.

It must be a Seattle thing..but 5e took a page from Steve Balmer, ex-Executive of Microsoft. 5e D&D's mantra is that:
"Confusing rules language is a feature not a bug".

(I hate this....the 2e core books were so much better at using natural language to explain game concepts than 5e)

I disagree with Unoriginal. Flavor text is the portion of an ability than can be changed with minimal fuss and bother. The verbiage of "a veil of shadow and silence" that is used for the Pass Without Trace spell can easily be altered, without much or any impact to game play.

[Unoriginal]

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I disagree with Unoriginal. Flavor text is the portion of an ability than can be changed with minimal fuss and bother. The verbiage of "a veils of shadow and silence" that is used for the Pass Without Trace spell can easily be altered, without much or any impact to game play.

Then you are not using RAW. Absolutely nothing wrong with that, but it needs to be acknowledged.

[Segev]

I disagree with Unoriginal. Flavor text is the portion of an ability than can be changed with minimal fuss and bother. The verbiage of "a veil of shadow and silence" that is used for the Pass Without Trace spell can easily be altered, without much or any impact to game play.

Refluffing something doesn't make it break, but it is a change.

[Unoriginal]

Refluffing something doesn't make it break, but it is a change.

Indeed. And one can always argue that it can have effects mechanically.


For example, Pass Without a Trace could be argued to not work in the Demiplane of Drem the ancient solar deity, where no shadow exists or can exist, due to the "a veil of shadow and silence" wording.

[FrancisBean]

Now that we've gotten (I hope!) most of the "you're just reading it wrong" out of our systems, I think it should be clear that there really are some conflicting interpretations. I don't have a particular dire wolf in that cage match, and I could happily argue either side of it. With a gun to my head I'd admit that I actually prefer a strict interpretation of "target" in relationship to spells. That's become something of a linchpin in a number of other rulings such as the Twinned metamagic and so forth, so I'd be reluctant to extend the definition of "target" to creatures who are merely impacted by the spell effects.

But getting to some of the more clear-cut issues, does it really make sense that being under Nondetection means you can't cast Commune? (Technically, you can cast it and waste the slot, but it has no effect; XGtE pg 85-86.) You can't get the benefits of Guidance? That's very clear under RAW, and I still see that as a mess. Are there any good reasons not to just ignore that consequence of the spell text?

[Dr.Samurai]

It says "magic", not "spell". I read it that someone under the effect of a divination spell like See Invisibility cannot target you with that magic. In this context, target is less a mechanical term and more colloquial (select as an object of attention or attack). Meaning, you cannot be the object of attention of divination magic.

[Unoriginal]

Now that we've gotten (I hope!) most of the "you're just reading it wrong" out of our systems, I think it should be clear that there really are some conflicting interpretations.

There's always conflicting interpretations. Which is why I argue there is nothing such as Rules as Written, only Rules as Read.




But getting to some of the more clear-cut issues, does it really make sense that being under Nondetection means you can't cast Commune? (Technically, you can cast it and waste the slot, but it has no effect; XGtE pg 85-86.) You can't get the benefits of Guidance? That's very clear under RAW, and I still see that as a mess. Are there any good reasons not to just ignore that consequence of the spell text?

Define "good reasons".

Does it make the spell more practical to use? No.

Does it makes the spell have a bigger number of limitations? Yes.

Does it makes the spell weirder? Yes.

Some people like it when spells are weird and have peculiar limitations. Others (and I assume said others to be a significantly larger group) prefers it when spells have as few limits as possible.

So which option is the more enjoyable depends of who you are and with whom you play.

[Thunderous Mojo]

Segev and Unoriginal..I did say "minimal fuss and bother".😀
Of course a DM has control over what the "in game effects are".

Segev and I had a discussion regarding the text of PWoT, last week, (I believe), in the "let's abuse PWoT" thread.

I used the example of crossing the plains of New Mexico and Texas following old Route 66. I commented that in some campaigns, noticing a patch of shadow moving across the plains on a cloudless day, could all on it's own draw the active attention of something that noticed the shadow.

Personally, I think while it is fine to have location effects that alter or inhibit how powers work, the players should mostly be informed of these changes, in advance of them confirming they cast the spell.

*note I say mostly, because sometimes, it is entirely appropriate to have some environmental effect only became apparent upon a completed casting or spell fizzle*

[MaxWilson]

Personally, I think while it is fine to have location effects that alter or inhibit how powers work, the players should mostly be informed of these changes, in advance of them confirming they cast the spell.

I agree in principle that players should know how their own spells work including any intentional changes from RAW (e.g. "at this table, Simulacrum produces a copy of the original with only 50% of the original's power/levels/HP/etc., but it can regain spell slots as normal"). The rules written in the PHB are important mostly as a shared reference point.

In practice it's not possible to identify all conflicting rules interpretations up front, and a lot of the burden for preventing surprises has to rest on the player--if you're not sure how your DM is going to run a particular spell, like Darkness or Nondetection, it would be a good idea to have a rules conversation up front with the DM and/or the entire table (ideally between game sessions or before a game session starts) so you can avoid having any surprises during the middle of a game session. And in the cases where the conflict is a surprise to everyone, the burden is then on the DM and the players to be charitable to each other and find something that works for everybody, even if it's just an ad hoc ruling that everyone understands is not setting a precedent for the future.

[FrancisBean]

...and back to the original question, for those of you who have had it come up, how have you handled it in your own games? I can see it's going to come up in my game in some significant ways, and I want to get my rulings ready ahead, and be ready to tell my players in advance anything they need to know beforehand.

Yes, it's all about what works best at your individual table, but I'm looking for a sampling of what has worked at other tables. Or just as important, what hasn't worked. Cautionary tales are always valuable.

[Segev]

Now that we've gotten (I hope!) most of the "you're just reading it wrong" out of our systems, I think it should be clear that there really are some conflicting interpretations. I don't have a particular dire wolf in that cage match, and I could happily argue either side of it. With a gun to my head I'd admit that I actually prefer a strict interpretation of "target" in relationship to spells. That's become something of a linchpin in a number of other rulings such as the Twinned metamagic and so forth, so I'd be reluctant to extend the definition of "target" to creatures who are merely impacted by the spell effects.

But getting to some of the more clear-cut issues, does it really make sense that being under Nondetection means you can't cast Commune? (Technically, you can cast it and waste the slot, but it has no effect; XGtE pg 85-86.) You can't get the benefits of Guidance? That's very clear under RAW, and I still see that as a mess. Are there any good reasons not to just ignore that consequence of the spell text?

The intention and the wording both align: it keeps you from being detected. You can't be targeted by divination magic that would detect you. It doesn't prevent you from being targeted by spells that aren't related to detection. That's how I'd run it, and that seems in line with the wording of the spell as read in common colloquial English.

[LudicSavant]

I run it by RAW (e.g. it doesn't prevent See Invisibility from working) and just accept that it's niche. It prevents scrying and is useful to prevent Mind Flayer Elder Brains from pinpointing you, if you're going into Mind Flayer territory.

For anything else you'll have to research a custom spell, which I have rules for and encourage players to do.

What are your rules for researching custom spells?

[Amdy_vill]

Countering more than one is powerful so the downside of not being able to use good divination spells seems intended.it also seems intended that it should stop things like see invisible because if it only shut down positive spells and allowed negative spells to pass through it would be a "Trap spell" Like true strike and I prefer to think that WotC Made a minimal amount of "trap spells"

There is no such thing as "fluff" in 5e spell description. What happens is what is described to happen.

You're just wrong, both the dmg and Tasha talk about the "Fluff" text and how you can change it. it was an advertised feature of tashas. tho it was a bad portion of the book. dnd as a game has a problem of placing fluff text on everything and not making it clear where it ends. you can argue about where the fluff text ends on nondetection but almost everything in 5e has some fluff text attached to it.

[Mellack]

It says "magic", not "spell". I read it that someone under the effect of a divination spell like See Invisibility cannot target you with that magic. In this context, target is less a mechanical term and more colloquial (select as an object of attention or attack). Meaning, you cannot be the object of attention of divination magic.

I agree with the doctor here. I think it is being too RAW in the reading in assuming that "target" must always and only be used in the technical term of referring to the target line of a spell. We know that the writers were going for a more natural language style, and I think this is a case of them doing that and being somewhat inexact. In my game we determined that a nondetection protected subject simply doesn't show on any detection spell.

[MaxWilson]

What are your rules for researching custom spells?

They basically mirror AD&D spell research rules from the Complete Wizard's Handbook. The bulk of the rules are oriented around how to do the research, not how to design the spell (that's still a subjective judgment by DM and player based on analogy to existing spells).

Here goes though for those who care:


First step: Design. Propose a spell to the DM including components, casting time, AoE, effect, etc. DM will tell you if the spell is possible, and what the effective level of the spell is based on analogies to existing spells. You and the DM discuss any tweaks you'd like to make to the proposed spell to raise or lower the level, e.g. adding a concentration requirement might lower the effective level by perhaps -2 spell levels (based on looking at Protection From Evil vs. Magic Circle), whereas changing the casting time to a bonus action might raise it by +1 or +2 levels (based on looking at Misty Step vs. Dimension Door). Note: this is not necessarily the slot you will need to use to cast the spell. That's determined in step #3 below, slot optimization.

Second step: Acquire Library. Get access to a spell research library of the appropriate effective level. For a spell of effective level N, you need access to a research library worth at least N^2 * 1000 gp. (Half the money you spend on research adds to the permanent value of the library, as you buy esoteric treatises and arcane reference libraries, etc.) To research a 5th level spell, you need to invest 25,000 gp or more in building your research library, or join a magical college or organization that will grant you access to theirs.

Third step: Slot Optimization. Decide how heavily you want to optimize the spell relative to its effective level. This will affect the difficulty of research. If you don't care about the spell slot cost, you can use brute-force techniques to quickly and reliably research a spell that gets the job done but isn't usable by low-level mages. Drawmij's Instant Summons probably is 6th level because some lazy archmage brute-forced the spell research for his own personal one-off use--I'd call it effectively 4th level in power if you drop the ritual tag, 3rd once you consider the expensive material component. A PC could re-invent Drawmij's Instant Summons as a 3rd level spell pretty easily, if they had a reason to. Conversely, Fireball is effectively about 5th level IMO but was optimized by someone long ago to be cast from a 3rd level slot--it would be hard to re-invent Fireball without raising the level. Spells cannot be optimized by more than 50% of their effective level--there are no 2nd level Fireballs allowed.

Fourth step: Trial and Error. Research the spell over the course of several weeks or months. You must spend all of your creative energies on research during this time, typically working eight to twelve hours a day and avoiding distractions like adventuring. Every week you must pay N*100 gp where N is the effective spell level (and half that money goes towards increasing the permanent value of your research library) and must make a successful Intelligence (Arcana) checks (no matter whether you're a wizard or sorcerer or cleric or warlock or whatever) of DC 10 + N + [optimization penalty], where the optimization penalty is 4 * [effective level - researched level]. After 2 failures, the version of the spell you're researching acquires a quirk which the DM will inform you of (an unintended change), unless you opt to start over. After 3 failures, the research has hit a dead end and must be started over from the beginning. Otherwise, after N successes, the spell research completes and you now know and/or have memorized the spell and can write it in your spellbook if you have one, discarding another spell you know or have memorized if you are over the limit for your current class/level.

Example:

For example, re-researching Fireball as a 4th level spell would require a level 5 research library (25,000 gp) and 5 weeks of successful DC 10 + 5 (effective level 5) + 4 (optimization penalty) = DC 19 Int (Arcana) checks at a cost of 500 gp per week, and each week of research increases the value of your library by 250 gp.

Re-researching a poison-based version of Melf's Acid Arrow (effective level 1, actual level 2) would require a level 1 research library (1000 gp) and 1 week with a DC 11 - 4 = DC 7 Int (Arcana) check, 1 success required, at a cost of 100 gp that week (with 50 gp going towards increasing the library's value).

[LudicSavant]

They basically mirror AD&D spell research rules from the Complete Wizard's Handbook. The bulk of the rules are oriented around how to do the research, not how to design the spell (that's still a subjective judgment by DM and player based on analogy to existing spells).

Here goes though for those who care:


First step: Design. Propose a spell to the DM including components, casting time, AoE, effect, etc. DM will tell you if the spell is possible, and what the effective level of the spell is based on analogies to existing spells. You and the DM discuss any tweaks you'd like to make to the proposed spell to raise or lower the level, e.g. adding a concentration requirement might lower the effective level by perhaps -2 spell levels (based on looking at Protection From Evil vs. Magic Circle), whereas changing the casting time to a bonus action might raise it by +1 or +2 levels (based on looking at Misty Step vs. Dimension Door). Note: this is not necessarily the slot you will need to use to cast the spell. That's determined in step #3 below, slot optimization.

Second step: Acquire Library. Get access to a spell research library of the appropriate effective level. For a spell of effective level N, you need access to a research library worth at least N^2 * 1000 gp. (Half the money you spend on research adds to the permanent value of the library, as you buy esoteric treatises and arcane reference libraries, etc.) To research a 5th level spell, you need to invest 25,000 gp or more in building your research library, or join a magical college or organization that will grant you access to theirs.

Third step: Slot Optimization. Decide how heavily you want to optimize the spell relative to its effective level. This will affect the difficulty of research. If you don't care about the spell slot cost, you can use brute-force techniques to quickly and reliably research a spell that gets the job done but isn't usable by low-level mages. Drawmij's Instant Summons probably is 6th level because some lazy archmage brute-forced the spell research for his own personal one-off use--I'd call it effectively 4th level in power if you drop the ritual tag, 3rd once you consider the expensive material component. A PC could re-invent Drawmij's Instant Summons as a 3rd level spell pretty easily, if they had a reason to. Conversely, Fireball is effectively about 5th level IMO but was optimized by someone long ago to be cast from a 3rd level slot--it would be hard to re-invent Fireball without raising the level. Spells cannot be optimized by more than 50% of their effective level--there are no 2nd level Fireballs allowed.

Fourth step: Trial and Error. Research the spell over the course of several weeks or months. You must spend all of your creative energies on research during this time, typically working eight to twelve hours a day and avoiding distractions like adventuring. Every week you must pay N*100 gp where N is the effective spell level (and half that money goes towards increasing the permanent value of your research library) and must make a successful Intelligence (Arcana) checks (no matter whether you're a wizard or sorcerer or cleric or warlock or whatever) of DC 10 + N + [optimization penalty], where the optimization penalty is 4 * [effective level - researched level]. After 2 failures, the version of the spell you're researching acquires a quirk which the DM will inform you of (an unintended change), unless you opt to start over. After 3 failures, the research has hit a dead end and must be started over from the beginning. Otherwise, after N successes, the spell research completes and you now know and/or have memorized the spell and can write it in your spellbook if you have one, discarding another spell you know or have memorized if you are over the limit for your current class/level.

Example:

For example, re-researching Fireball as a 4th level spell would require a level 5 research library (25,000 gp) and 5 weeks of successful DC 10 + 5 (effective level 5) + 4 (optimization penalty) = DC 19 Int (Arcana) checks at a cost of 500 gp per week, and each week of research increases the value of your library by 250 gp.

Re-researching a poison-based version of Melf's Acid Arrow (effective level 1, actual level 2) would require a level 1 research level (1000 gp) and 1 week with a DC 11 - 4 = DC 7 Int (Arcana) check, 1 success required, at a cost of 100 gp that week (with 50 gp going towards increasing the library's value).

Interesting. Thank you for the detailed answer!

[Keravath]

Personally, I play non-detection pretty much as it is written in my games. The target of non-detection is hidden from divination magic and can't be targeted by divination spells or scrying sensors.

Does that mean an invisible creature under a non-detection can not be seen by a creature using true sight or see invisible? Absolutely yes.

However, if the creature actually wants to be undetected they have to succeed on a hide check (stealth) since otherwise they are still giving away their position either by sound, air motion, tracks, interactions with the environment or something else. Invisibility in 5e isn't an automatic hidden "I win" button that it often was in previous editions. Being unseen just fulfills a requirement for making a hide check to determine whether the creature's location is still known or not.

Being under both non-detection and invisibility is exactly the same as just having invisibility whether the creatures doing the looking have truesight or see invisible or not. The creature isn't any easy or harder to detect using regular senses than it is without non-detection. All the non-detection does is block the various divination spells that might be used to obtain information about the creature under the non-detection.

In the case of the invisible non-detection assassin, they still have to succeed on a stealth check in order to approach unseen and unheard. Cover the floor with potato chips or the equivalent and the assassin may find it very difficult to approach silently.

[Thunderous Mojo]

In practice it's not possible to identify all conflicting rules interpretations up front, and a lot of the burden for preventing surprises has to rest on the player--if you're not sure how your DM is going to run a particular spell, like Darkness or Nondetection, it would be a good idea to have a rules conversation up front with the DM and/or the entire table (ideally between game sessions or before a game session starts) so you can avoid having any surprises during the middle of a game session. And in the cases where the conflict is a surprise to everyone, the burden is then on the DM and the players to be charitable to each other and find something that works for everybody, even if it's just an ad hoc ruling that everyone understands is not setting a precedent for the future.
I agree with this. No "session zero" can cover all spells, and frankly players would forget most of the information if it did. Having the character realize something like "In the land of the Sun King of the Sixth Heaven...shadows don't exist, and thus you know Pass Without Trace won't function" is fine.

[clearstream]

tl;dr: How do you handle Nondetection in your own games?

Here’s where I’m leaning. You can still choose to be affected by Self and Touch spells cast directly on you. Being “hidden” from divination for location/detection spells means you just don’t register as what it locates or detects. For See Invisibility and True Seeing, the spells show a vague, blurred empty space with Disadvantage on Perception. You can't see any details about an undetectable, invisible creature, but you have a chance to notice that something's there. For something like our Lich in disguise, Legend Lore would still work to give details about the Lich from the time periods when Nondetection wasn’t active, but wouldn’t help at all with periods under Nondetection. Scrying sensors don’t “see” you, but they see the vague blur as with See Invisibility, so the scryer knows there’s something they can’t make out. Foresight is 9th level, so I'm inclined to ignore consistency and just say it wins by raw power.
I RAI it a little differently from other posters, as follows


You hide the target from divination magic. I RAI that as entailing the target is hidden from such magic, benefiting from the rules of hiding: they count as hidden with no further roll needed from becoming seen or heard, or their location known, through divination magic.
The target can't be targeted by divination magic. To avoid arbitrating throughout the rules as to when "target" etc is a keyword and when it is colloquial, I read it consistently as a keyword. That does mean the target won't be able to be targeted by further divination magic, some of which could be beneficial. I find that straightforward to narrate in-world - to my satisfaction at least - for example, with guidance, the gods cannot guide a creature that they cannot divine the actions of, and so on.
The target can't be perceived through magical scrying sensors. I RAI that this extends even to things that don't involve divination magic, such as magic mouth. That spell can't be set up to trigger on the presence of a creature benefiting from nondetection.

I don't find spells like detect evil and good problematic, although there is obviously room for doubt about whose specific beats whose!? I RAI that the first effect of nondetection defeats the first of detect evil and good, because you can't know where a creature benefiting from nondetection is located if the only way you know that is by virtue of divination magic. I am there ruling that nondetection is narrower than detect evil and good on the grounds that the former is hiding one specific creature, while the latter is finding all creatures of six different types.

[Samayu]

"I want to know if that guy is undead. Divine Sense."
"There are no undead in the room."

The spell reads "you hide a target that you touch from divination magic." You're using divination magic to determine the nature of a target. That target is shrouded by Nondetection. Your Divine Sense fails.

I see no reason to nerf an underutilized spell just because you're not specifying a target of your magical ability. There is a potential target of your inquiry - that guy standing in front of you. I'm not using the word "target" in the very precise sense that it is used in Magic: The Gathering, it's a more general understanding.

I'd be more concerned about the definition of magic for the purposes of this spell. Like, is a creature's truesight magical? I played a gnome through CoS, and only used my Gnome Cunning twice, because all of the fear abilities were undead traits and not magical effects, according to my DM. Didn't seem right...

[Sigreid]

I play it very simple. If you don't know the person under the effect of Non-Detection is there/right were they are, Magic isn't going to give you that information.

[FrancisBean]

"I want to know if that guy is undead. Divine Sense."
"There are no undead in the room."

The spell reads "you hide a target that you touch from divination magic." You're using divination magic to determine the nature of a target. That target is shrouded by Nondetection. Your Divine Sense fails.

I'm guessing that you'd also rule that True Seeing wouldn't fail in an obvious way, either... That they'd just see what their eyes see, and wouldn't get additional information from the divination. Detect Thoughts, OTOH, would be a giveaway because the spell would refuse to even admit that there's a thinking creature present. Nondetection wouldn't create fictional surface thoughts. That holds open the option of researching some sort of custom spell for projecting surface thoughts, if someone really wants that added ability. It's a pretty solid interpretation, and easier to make internally self-consistent than mine. I may use yours, instead.

What are your thoughts on how the scrying sensor fails? It just doesn't "see" anything there, or something a little more obvious like, "you can't seem to make your sensor face that direction, can't get the right angle on your camera, &c.?"

[Samayu]

True Seeing, yeah, I think that makes sense.

Detect Thoughts, absolutely. I don't see a problem with "oh, he's shrouded, somehow?" "I don't know. He could be an illusion." Note: I find it very strange that this 2nd level spell has no save, for surface thoughts.

For Scrying, the spell would just fail. Because this one really does target your target, so if you can't target them, the spell wouldn't work. It would be as if the target made their save. Which brings up the question whether spellcasters know when their target succeeded on a save. If this is known, then they would also know that the target didn't make their save, and that the spell failed for some other reason.

I don't think it's a big deal that someone finds out you have Nondetection on you, because they're trying to read your thoughts. With mindreading spells at 2nd level, I'd be casting Nondetection all the time!

[Samayu]

Going down the list of divination spells...

Tongues. "This spell grants the creature you touch the ability to understand any spoken language it hears. Moreover, when the target speaks, any creature that knows at least one language and can hear the target understands what it says."
If you're using tongues, and someone else has Nondetection, does this mean you can't understand them if you were relying on the spell? You only hear that other language that you can't understand. I guess that makes sense.

Arcane Eye. "You create an invisible, magical eye within range that hovers in the air for the duration. You mentally receive visual information from the eye, which has normal vision and darkvision out to 30 feet. The eye can look in every direction." And you can move it around. Clairvoyance has similar issues.
So you move the eye into a room, and there's a Nondetectable person there. It's as if they're invisible? What if it was placed on an entire (small) room? Does the room appear empty? Or... blank? Like a black hole. "I'm sick of those kids always scrying me on the toilet, and then posting to it the whole school on the Telepathic Bond network! In my day, we made up our own pictures with Minor Illusion."

Hey, you can put Nondetection on your invisible sensors, can't you?

Legend Lore is an odd spell. It's not really clear where the info comes from, but it's not a mindreading spell. The info comes from the world. The spell description says "lore that has never been widely known" which indicates the the info is known by someone. The thing in question must be of legendary importance, so that's odd too. Anyway, I think this is one divination spell which is not affected by Nondetection.

[Rara1212]

"I want to know if that guy is undead. Divine Sense."
"There are no undead in the room."

The spell reads "you hide a target that you touch from divination magic." You're using divination magic to determine the nature of a target. That target is shrouded by Nondetection. Your Divine Sense fails.

I see no reason to nerf an underutilized spell just because you're not specifying a target of your magical ability. There is a potential target of your inquiry - that guy standing in front of you. I'm not using the word "target" in the very precise sense that it is used in Magic: The Gathering, it's a more general understanding.

I'd be more concerned about the definition of magic for the purposes of this spell. Like, is a creature's truesight magical? I played a gnome through CoS, and only used my Gnome Cunning twice, because all of the fear abilities were undead traits and not magical effects, according to my DM. Didn't seem right...

Isn't Divine Sense just an ability, so it's not Divination Magic at all? It's more like you getting a specialized organ for smelling/hearing those certain creature types.

[kazaryu]

tl;dr: How do you handle Nondetection in your own games?

Here’s where I’m leaning. You can still choose to be affected by Self and Touch spells cast directly on you. Being “hidden” from divination for location/detection spells means you just don’t register as what it locates or detects. this seems fair, i'd even extend it to any spell. you can choose to be affected so long as you know you're being 'targeted' so to speak.


For See Invisibility and True Seeing, the spells show a vague, blurred empty space with Disadvantage on Perception. You can't see any details about an undetectable, invisible creature, but you have a chance to notice that something's there.
rather than doing a half measure like this (where the spells meet in the middle) i'd suggest leaning one way or the other, and be very clear which way to go. alternatively go with spell level contests. a 3rd level nondetection completely trumps a 2nd level see invisibility, but not 6th level true seeing. maybe do an opposed caster roll for ties? or for streamlining you can do it as is. the problem with the meet in the middle approach, imo, is that it means both spells are less effective when they meet each other. thus defeating the reason the spell was cast in the first place.



For something like our Lich in disguise, Legend Lore would still work to give details about the Lich from the time periods when Nondetection wasn’t active, but wouldn’t help at all with periods under Nondetection idk, makes more sense that legend lore would fail if cast on a person under Nondetection. but succeed normally if not. idk why nondetection would have a permanent effect like that.


. Scrying sensors don’t “see” you, but they see the vague blur as with See Invisibility, so the scryer knows there’s something they can’t make out. this one, in particular, i dislike. because it allows scrying-esque spells like arcane eye, to still follow a person under the effects of nondetection. which seems counter to the intent of the spell. sure, if 2 people are having a conversation and 1 of them is undetectable, it looks odd...but thats the point. it should. who is that npc talking to? what are they saying? oh..did they leave? ****! where did they go!?. im honestly not sure why you'd nerf the spell like that.


For Scrying, the spell would just fail. Because this one really does target your target, so if you can't target them, the spell wouldn't work. It would be as if the target made their save. Which brings up the question whether spellcasters know when their target succeeded on a save. If this is known, then they would also know that the target didn't make their save, and that the spell failed for some other reason. don't froget, scrying can also target a location, not just a person. so its possible to have a scrying active, and a non-detection person walks into your FoV. i think thats what OP was referring to

[FrancisBean]

For Scrying, the spell would just fail. Because this one really does target your target, so if you can't target them, the spell wouldn't work. It would be as if the target made their save. Which brings up the question whether spellcasters know when their target succeeded on a save. If this is known, then they would also know that the target didn't make their save, and that the spell failed for some other reason.

As I think someone else mentioned in the thread, a scrying sensor could be targetting a room, or someone else in the room, in which case it wouldn't just fail. Related: XGtE, pg85-86 addresses the matter of failures due to ineligible targets. If the spell can be negated by a saving throw, it's treated as if the target made the save. It's only in cases where there's no save that the caster gets told about an unexpected failure.

Narratively, I'm kinda liking the notion that you just can't get your scrying sensor to view someone nondetectable. For anybody old enough to remember the books, I'm picturing it the way Watt-Evans handled scrying on the Forgotten King in "The Lords of Dus" series. You could sort of follow along by watching someone else, and maybe sometimes you could catch a glimpse of the corner of his clothing, but the spell just wouldn't focus on the Forgotten King himself. It might not be consistent with the other rulings, but the way it sets a scene is spiff.

[Segev]

If you're using legend lore on somebody protected by nondetection, I would say it fails. If that person is just an ancillary part, then you'll get stuff not relating to him.