Detect Magic, Dispel Magic, and Magical Traps? How do they interact?

[Nikushimi]

Hey there, I have been in the process of creating encounters and puzzles for my group to eventually overcome, and I want to use more magical traps than mechanical traps.

Specifically, I have an encounter planned that is a room single chair in the center of it.

The chair is arranged in such a way that when one sits in it their field of view reveals the process of how to beat the room. The details of which are vague right now because I still need to flesh out what exactly the puzzle will be.

But, back to the chair.

When they sit in the chair a magical trap is activated which basically acts as a Hold spell, because they won't be able to move. It also erects a barrier around the chair and the person sitting in it so no outside force can interact with the person sitting in the chair. If they get the puzzle wrong while someone is in the chair, something happens to the person in the chair (unsure what yet).

The chair can be moved, but doing so activated invisible magical runes which yeet them from the room, doing some Force damage and resets the chair.

My question then is simple.

If someone casts detect magic will magical runes/symbols light up?

For example, the chair technically has a rune painted/carved into it underneath the cushion which is activated upon someone sitting on it. Only reacts to living beings (warforged included).

So, since the magic technically won't activate until they sit on the chair will detect magic give away the symbol even though the magic isn't active yet?

In other words, can Detect Magic determine inactive runes as "magical" or not? The magic activates after something happens.

The same with the invisible runes filling the entire chamber. Will detect magic show those invisible runes as well?
---

Onto the next part of the question.

If they somehow determine the place is magical, and they decide to cast Dispel Magic on the chair, the rune, or the invisible symbols how does it work? The magic is not active yet, but would it dispel the runes?

For example, if someone says "I'll cast Dispel Magic on the chair."

Well, the chair technically isn't magical, but would the rune be affected or would they have to specifically target the rune underneath the cushion of the chair?

And on another note. A quite simple question. How does dispel magic work on magical traps? Does it get rid of the trap or just disable to magic for a short time?

Thanks in advance!

[JackPhoenix]

Well, you're the GM, so it's up to you, obviously, but it sounds like Detect Magic should be able to detect the runes.... they are there and magical, even if they are just in "standby mode" instead of having an active effect triggered.

Dispel Magic only work on spells, not magic items or other magical effects. Unless the trap is a spell (Glyph of Warding?), it doesn't interact with it.

[Lunali]

Well, you're the GM, so it's up to you, obviously, but it sounds like Detect Magic should be able to detect the runes.... they are there and magical, even if they are just in "standby mode" instead of having an active effect triggered.

Dispel Magic only work on spells, not magic items or other magical effects. Unless the trap is a spell (Glyph of Warding?), it doesn't interact with it.

Dispel explicitly works on magical effects, but the spell text is unclear as to whether it is automatically successful or, if not, what to roll against for non-spells.

[JackPhoenix]

Dispel explicitly works on magical effects, but the spell text is unclear as to whether it is automatically successful or, if not, what to roll against for non-spells.

You can target magical effect.... like a Wall of Fire or a Fog Cloud, neither is an creature or an object... but it only ends spells. If there's no spell on the target, it does nothing.

[Christew]

You can target magical effect.... like a Wall of Fire or a Fog Cloud, neither is an creature or an object... but it only ends spells. If there's no spell on the target, it does nothing.
Yeah, this.
Dispel Magic: "Choose any creature, object, or magical effect within range. Any spell of 3rd Level or lower on the target ends."

[Nikushimi]

So, with Dispel Magic, if I'm understanding correctly, by RAW it will NOT dispel the trap or the room?

It only works on active effects and objects? So the rune does not count as an object?

I recently watched a game where a player used Dispel Magic on a lock, which broke the Arcane Lock on it. While the Arcane Lock is not a trap it brought this question to mind about magical traps.

So let's say you have an Arcane Lock on the lock, but also have a magical trap on the lock. Let's say...a magical cone of fire spews forth upon tampering with it kind of trap.

If they cast Dispel Magic on the lock would both the Arcane Lock and technically Burning Hands trap be dispelled or only the arcane lock?

I know I am the DM, and can make the call, BUT I want to stick to the rules as much as possible and understand them enough to explain why the Dispel Magic won't work, or why it doesn't on this particular set up.

Which is why I brought the question here.

[Man_Over_Game]

I know I am the DM, and can make the call, BUT I want to stick to the rules as much as possible and understand them enough to explain why the Dispel Magic won't work, or why it doesn't on this particular set up.

So I'm a player. I smell something fishy and I cast Detect Magic. I can detect the fact there's dormant magic radiating from the chair, but the DM won't tell me what it is. I squint my eyes, rolled an Arcana check, failed an Arcana check, decide that paranoia never hurt anyone, and cast Dispel Magic on the chair. DM says that it appears that nothing happened, and my Detect Magic is still reading something. Huh. Well, I gave it all I got. I sit in the chair.

So despite doing pretty much everything right, you're going to tell me that I did it wrong. Good DMing sometimes requires you to ignore the text.

If you want your players to be investigative and do things like study puzzles and preemptively use things like Detect Magic, you need to reward that. Sometimes overly so. I've gotten into the habit of rewarding players more for their non-combat spells than I would for their combat spells, because otherwise why should I expect them to invest in things like Plant Growth or Gentle Repose that add to the world? It's been a challenge to make something like Gaseous Form more valuable than Fireball, but I'd rather that be my problem than theirs.

[Christew]

So, with Dispel Magic, if I'm understanding correctly, by RAW it will NOT dispel the trap or the room?

It only works on active effects and objects? So the rune does not count as an object?

I recently watched a game where a player used Dispel Magic on a lock, which broke the Arcane Lock on it. While the Arcane Lock is not a trap it brought this question to mind about magical traps.

So let's say you have an Arcane Lock on the lock, but also have a magical trap on the lock. Let's say...a magical cone of fire spews forth upon tampering with it kind of trap.

If they cast Dispel Magic on the lock would both the Arcane Lock and technically Burning Hands trap be dispelled or only the arcane lock?

I know I am the DM, and can make the call, BUT I want to stick to the rules as much as possible and understand them enough to explain why the Dispel Magic won't work, or why it doesn't on this particular set up.

Which is why I brought the question here.
Dispel Magic is mostly for ending magic effects in combat (debuffs, magic walls, etc). It's only real interaction with traps is through lingering effects like glyph of warding or as you mentioned, arcane lock. So if you are using a non spell magic effect for your trap, Detect Magic would reveal that it is magical, but Dispel Magic would not disrupt it. I would say that you should telegraph this through a reasonable Arcana check (ie your knowledge of the arcane gives you no insight into what magic is at work here, but you know that it is like no spell you have ever seen, or some such). Burning a third level spell over confusing description sucks.

Per having both an arcane lock and a glyph of warding: burning hands on the same lock, both would be dispelled with a single casting of Dispel Magic. "Any spell of 3rd level or lower on the target ends.". Arcane lock is 2nd level and glyph of warding is 3rd level. You should generally stick to using glyph of warding for spell traps specifically so that it can be dispelled. If you just say "burning hands trap" it is unclear if there is a spell to be dispelled or not. For example, a mechanical trap that used oil an a flint to deal the same damage effect as burning hands would not be subject to dispel magic.

[Lunali]

So, with Dispel Magic, if I'm understanding correctly, by RAW it will NOT dispel the trap or the room?

It only works on active effects and objects? So the rune does not count as an object?

I recently watched a game where a player used Dispel Magic on a lock, which broke the Arcane Lock on it. While the Arcane Lock is not a trap it brought this question to mind about magical traps.

So let's say you have an Arcane Lock on the lock, but also have a magical trap on the lock. Let's say...a magical cone of fire spews forth upon tampering with it kind of trap.

If they cast Dispel Magic on the lock would both the Arcane Lock and technically Burning Hands trap be dispelled or only the arcane lock?

I know I am the DM, and can make the call, BUT I want to stick to the rules as much as possible and understand them enough to explain why the Dispel Magic won't work, or why it doesn't on this particular set up.

Which is why I brought the question here.

If they cast dispel magic it would dispel both the arcane lock and the glyph of warding housing the burning hands spell.

As for why dispel magic won't work, it's a magical item, dispel works on active effects but won't prevent the activation of an item. The downside of this approach is that once the puzzle is finished, it is still a magical item and is potentially loot.

[Man_Over_Game]

Dispel Magic is mostly for ending magic effects in combat (debuffs, magic walls, etc). It's only real interaction with traps is through lingering effects like glyph of warding or as you mentioned, arcane lock. So if you are using a non spell magic effect for your trap, Detect Magic would reveal that it is magical, but Dispel Magic would not disrupt it. I would say that you should telegraph this through a reasonable Arcana check (ie your knowledge of the arcane gives you no insight into what magic is at work here, but you know that it is like no spell you have ever seen, or some such). Burning a third level spell over confusing description sucks.

Per having both an arcane lock and a glyph of warding: burning hands on the same lock, both would be dispelled with a single casting of Dispel Magic. "Any spell of 3rd level or lower on the target ends.". Arcane lock is 2nd level and glyph of warding is 3rd level. You should generally stick to using glyph of warding for spell traps specifically so that it can be dispelled. If you just say "burning hands trap" it is unclear if there is a spell to be dispelled or not. For example, a mechanical trap that used oil an a flint to deal the same damage effect as burning hands would not be subject to dispel magic.

At the same time, if it's ambiguous to their DM, how is the player going to feel?

Don't wait for your players to make a solution. If you can't think of a few for your players to come up with, then that implies that there isn't enough information you're giving them to solve the problem.

The reason puzzles are often hated by players is because they usually are a scenario where the players have to think like their DM, not the DM thinking like his players. If the players aren't supposed to use Dispel Magic, what do you expect them to do? I'm not saying that the chair trap is a bad idea, but it seems like there's a lot of investment into disabling it through Dispel Magic for it to be a secondary solution.

[JackPhoenix]

So I'm a player. I smell something fishy and I cast Detect Magic. I can detect the fact there's dormant magic radiating from the chair, but the DM won't tell me what it is. I squint my eyes, rolled an Arcana check, failed an Arcana check, decide that paranoia never hurt anyone, and cast Dispel Magic on the chair. DM says that it appears that nothing happened, and my Detect Magic is still reading something. Huh. Well, I gave it all I got. I sit in the chair.

So despite doing pretty much everything right, you're going to tell me that I did it wrong. Good DMing sometimes requires you to ignore the text.

If you want your players to be investigative and do things like study puzzles and preemptively use things like Detect Magic, you need to reward that. Sometimes overly so. I've gotten into the habit of rewarding players more for their non-combat spells than I would for their combat spells, because otherwise why should I expect them to invest in things like Plant Growth or Gentle Repose that add to the world? It's been a challenge to make something like Gaseous Form more valuable than Fireball, but I'd rather that be my problem than theirs.

Speaking of rarely used spells, that's exactly why Identify exist.

[Chronos]

Right. Detect Magic should tell you that they chair is magical, and what school of magic it's most strongly associated with. But Identify should, by the rules, tell you everything important there is to know about it. Exceptions to this can exist (Identify won't notice that some items are cursed, and things like artifacts are probably special, and Nystull's Magic Aura can deceive it), but for the most part, it should tell you everything.

[Man_Over_Game]

Right. Detect Magic should tell you that they chair is magical, and what school of magic it's most strongly associated with. But Identify should, by the rules, tell you everything important there is to know about it. Exceptions to this can exist (Identify won't notice that some items are cursed, and things like artifacts are probably special, and Nystull's Magic Aura can deceive it), but for the most part, it should tell you everything.

But there's two issues with that:


Identify is a lot harder to get access to than Detect Magic.
The DM didn't consider it, so why should have the players?

I'm not saying OP needs to consider everything, but if Identify was a spell that was something the players could be expected to try out of habit, he likely would have mentioned it.

My issue is that there's an expectation for a niche solution. "If you did it just right, and cast the spells in the elemental order given on the correct symbols, the traps wouldn't activate". No, that's silly. Expect a broad and accessible solution, and then make exceptions for niche and unique ideas.

Maybe that could be whatever the puzzle is, but I wouldn't set an expectation for the players to have a chance of getting information before starting the puzzle/trap.

[Nikushimi]

But there's two issues with that:


Identify is a lot harder to get access to than Detect Magic.
The DM didn't consider it, so why should have the players?

I'm not saying OP needs to consider everything, but if Identify was a spell that was something the players could be expected to try out of habit, he likely would have mentioned it.

My issue is that there's an expectation for a niche solution. "If you did it just right, and cast the spells in the elemental order given on the correct symbols, the traps wouldn't activate". No, that's silly. Expect a broad and accessible solution, and then make exceptions for niche and unique ideas.

Maybe that could be whatever the puzzle is, but I wouldn't set an expectation for the players to have a chance of getting information before starting the puzzle/trap.

You seem to be under the impression that I am attempting to prevent the use of Dispel Magic and Detect Magic. Making it futile.

That's not the case.

I am trying to figure out how Detect Magic, Dispel Magic, and Magical Traps/Runes interact with each other.

1. Dispel Magic states that it only dispels ACTIVE effects, so since these runes are not activated until certain conditions are met, then would it still dispel or not?

2. Detect Magic detects magical auras and other such effects, but does it work on inactive runes that do not activate their magic until certain conditions are met?

3. Would Detect Magic indicate that the chair is magical, or the rune drawn onto it? The chair is not imbued with magic. It just has the rune on it.

This is what I'm trying to figure out.

I am not attempting to make Dispel and Detect Magic useless. I am trying to figure out, by RAW, how this interaction would work. So I can explain it to my players should they attempt to find out any magic.
---

The puzzle itself breaks down into

"You enter the room. It's almost perfectly square. In the center of the room is one cushioned chair, placed perfectly in the middle of this room. On one side of the room is a bunch of blank cogs. What do you do?"

The point of it is to get them to investigate the one side of the room which contains part of the puzzle. P.s. The blank cog thing is just a placeholder to give you a picture of what I am attempting to do. Anyways....

They investigate the room, ask if there's any other doors to which the answer is "You can't seem to find or see any other door except the one you came in."

The trick to this is...it's the last room in the dungeon/vault/etc. This is to make them think there is something to this room.

The chair is suspicious so they investigate. Of course it's suspicious. It's in the center of the room and the only one there. Searching for traps, etc. Investigation will reveal the rune underneath the cushion.

At this point they'll probably try to tamper with the Rune or attempt to figure out what kind of Rune it is.

A successful Arcana would reveal what it does, and how.

However, if my players decide NOT to do an Arcana check and go straight to spells such as "Dispel Magic" or "Detect Magic" I want to know HOW that interacts with the Rune. Does it show it as magical? Does it not? Does it dispel it causing it to not work or not?

I need to know so I can properly play out the encounter for them.

Perhaps they don't investigate the chair and trying to search for another door they decided "Let's see if there's any illusions, I cast detect magic."

Will this reveal the runes around the room? Underneath the cushion? What about dispelling these runes?

That's what I'm trying to find out. I'm not trying to find out ways to make my players useless.

[Nikushimi]

But there's two issues with that:
Expect a broad and accessible solution, and then make exceptions for niche and unique ideas.


Also, as for this. I expect many different things to try, but if you are attempting to protect your vault full of treasure or library full of secrets would you want multiple different ways of entering and bypassing your security? No, of course not.

Now, if I know how Dispel Magic and Detect Magic, as well as other spells interact with such a room....then I can reward unique ideas that are not the wanted solution.

The one who made the room may have wanted them to sit in the chair and be forced to figure out the puzzle in time, or just to figure it out, but if they somehow find a hole in that, then it is rewarded.

But first I must know how certain interactions work so I can reward those various solutions that the original creator to the room did not anticipate.

I am not looking for broad solutions. That's what the players do. They break your puzzles.

I'm not trying to prevent any breaking of puzzles. I am trying to figure out the interaction between certain effects so I can properly make the puzzle and the room the way the person who created it intended. That person being me, but also the character in the world of mine who made it as a test to those who seek what it is guarding.

EDIT: Cause trust me, if I wanted to prevent multiple solutions, I could and I would, but I just want to know the interaction between these specific things.

[BloodSnake'sCha]

If you consider dormant magic as magic then detect magic will find it and with an action they will be able to learn it school.

A detect magic should be a good reason for you to ask for arcana check (some like "your senses tells you there is something of the arcane in here, roll an arcana check").

Identify should tell them what this singular rune do(maybe it only do the blocking the way out of the chair part, your choice).

Dispel magic should only work if it is a spell(like if the barrier around the chair is a wall of force(wall of force have different rules for dispel)).


House rule alart:
Personally I like to give items spell levels for dispelling the effect but make if 1d4 minutes suppression of the item but it is a house rule.

[swamp_slug]

As many of the posters before me have pointed out Dispel Magic only ends spells on the target.


Choose one creature, object, or magical effect within range. Any spell of 3rd level or lower on the target ends.

Now ask yourself this, how did this magical trap come into being? Someone had to mark the runes, so are the symbols themselves inherently magical, were they created with a magical paint (or other liquid) or (more likely IMO) just a focus for the spell that is cast into them?

In fact you keep using the word runes to describe this trap, that immediately makes me think that this is just a series of Glyph of Warding spells (or a variants of it). Glyph of Warding can contain a spell if its level or lower. I can also see a wizard coming up with a variant allowing it to store two or more different spells whose levels do not exceed that of the Glyph spell.

If your trap is just a series of Glyphs of Warding then Detect Magic should reveal them as the magic is present even if it hasn't been triggered, and Dispel Magic should end the effects.

Also, a thing to remember is that while the PHB and Xanathar's present a list of spells, these are not exhaustive lists of all magic in the multiverse. If you need a magic trap to have a specific effect that an existing spell does not produce, make up a spell for it and use its damage to determine its level, or for non-damaging spells compare its effects to other spells to get an appropriate level.

[Tes]

Found it important to put some rules/restrictions on magic detection.
Detect Magic won't just tell you everything magic there is to know about any given object (as pointed out by others, Identify probably could work though).

And it's important to communicate to the players that magic doesn't solve every problem by pushing a button. Especially against traps that would be designed with whoever setting them up being aware Detect Magic and Dispel Magic exists. The players will have to outsmart the effort that was used to set it up.

Basic door with a first level burning hands bound to evocation runes carved visibly in the frame? Well that's gonna be easy.

If there's a trapped door with magic runes inside the lock, designed to deactivate the trap, those are going to be tiny and hardly noticeable without taking a direct look into the lock. So it would require an Investigation check to figure out even with Detect Magic running. Lower DC for someone with Arcana Proficiency or Detect Magic running. Higher DC but still possible for i.e. the Rogue to notice that there is something that shouldn't be there.

Personally I'd allow someone to mess with the activation of a spell based trap if they can figure out how it's supposed to trigger. Multiple ways to do that, i.e. by damaging a physical component harboring the spell (probably not a good idea if the trap is Evocation or Necromany) or by disrupting the trigger with Dispel Magic. Big fan of having the guy with Arcana Proficiency and the guy with Thieves Tools Proficiency work together on magic traps.

Someone sufficiently powerful could always set up a very basic Spell but bind an upcast version into the trap to mess with someone who thinks they can be smart and get past it with a basic Dispel Magic.

If you really want to mess with people the occasional magic trap could even trigger only when Dispel Magic is cast on it. Otherwise it's just a mundane door.

[Man_Over_Game]

Also, as for this. I expect many different things to try, but if you are attempting to protect your vault full of treasure or library full of secrets would you want multiple different ways of entering and bypassing your security? No, of course not.

Now, if I know how Dispel Magic and Detect Magic, as well as other spells interact with such a room....then I can reward unique ideas that are not the wanted solution.

The one who made the room may have wanted them to sit in the chair and be forced to figure out the puzzle in time, or just to figure it out, but if they somehow find a hole in that, then it is rewarded.

But first I must know how certain interactions work so I can reward those various solutions that the original creator to the room did not anticipate.

I am not looking for broad solutions. That's what the players do. They break your puzzles.

I'm not trying to prevent any breaking of puzzles. I am trying to figure out the interaction between certain effects so I can properly make the puzzle and the room the way the person who created it intended. That person being me, but also the character in the world of mine who made it as a test to those who seek what it is guarding.

EDIT: Cause trust me, if I wanted to prevent multiple solutions, I could and I would, but I just want to know the interaction between these specific things.

Ah, I see. My bad!

People mentioned it before, but have you considered just using a Glyph of Warding?

"When you cast this spell, you inscribe a glyph that harms other creatures, either upon a surface (such as a table or a section of floor or wall) or within an object that can be closed (such as a book, a scroll, or a Treasure chest)...

The glyph is nearly Invisible and requires a successful Intelligence (Investigation) check against your spell save DC to be found.

You decide what triggers the glyph when you cast the spell. For glyphs inscribed on a surface, the most typical triggers include touching or standing on the glyph, removing another object covering the glyph, approaching within a certain distance of the glyph, or manipulating the object on which the glyph is inscribed...

When you inscribe the glyph, choose explosive runes or a spell glyph.

Spell Glyph: You can store a prepared spell of 3rd Level or lower in the glyph by casting it as part of creating the glyph. The spell must target a single creature or an area..."

[BurgerBeast]

1. Dispel Magic states that it only dispels ACTIVE effects, so since these runes are not activated until certain conditions are met, then would it still dispel or not?

Well, suppose the rune was a one-time effect. And consider its state before it is triggered and after it is triggered. What’s the difference?

It seems to me that one reasonable way to describe the rune is “active” before it is triggered and “inactive” afterward. So I think there is leeway, here. For example, how does the rune know if someone is sitting on it, or is close to it? That could be explained as some sort of active divination or abjuration effect.


2. Detect Magic detects magical auras and other such effects, but does it work on inactive runes that do not activate their magic until certain conditions are met?

That depends on your thoughts about what I said above. This is ultimately a question about how magic works in your world (the DM’s world). There’s no right answer, but you should aim for consistency.

I would personally make it detectable for the above reasons, only because it encourages player interaction.


3. Would Detect Magic indicate that the chair is magical, or the rune drawn onto it? The chair is not imbued with magic. It just has the rune on it.

I think you’re splitting hairs, here a bit. Obviously we can distinguish between the chair and the rune, but I’m not sure it’s a relevant distinction in this case. Is a scroll of fireball magical, or is only the ink on the scroll magical?


I need to know so I can properly play out the encounter for them.

I know I said this already so I apologize for being repetitive, but I think this is up to you and how magic works in your world. As long as you are consistent, you can do what makes sense for you.

I personally would want the use of spells that are appropriate to accomplish as much or more than an Arcana check, but I’m not “right” about that - it’s a preference.

[Mellack]

My understanding of how it should go:

Detect Magic will detect the rune.

Arcana check or Identify would tell what the rune does.

Dispel Magic would negate the rune. The rune certainly sounds like a spell rather than an magic item. It is running because it is searching for input.

You might also want to consider what happens if they just destroy the rune or chair.

[MoiMagnus]

1. Dispel Magic states that it only dispels ACTIVE effects, so since these runes are not activated until certain conditions are met, then would it still dispel or not?

The runes didn't appeared from nowhere. They were most likely from a spell you (implicitly) added to the universe. If you want to follow 5e logic, similarly to how Glyph of Warding can be dispelled even before the triggering conditions are met, you be able to dispel this trap even when the conditions are not yet met. [BTW, compare its power to Glyph of Warding to get an idea of the spell level. That will be relevant for dispel magic].

The other possibilities are a magic item (unless explicitly specified by the item, a magic item is immune to dispels of any kind) or an innate ability of a supernatural creature (in which case, the rune is not magical, it just happen to explode for supernatural reasons but that's not magic). But players will probably feel cheated on if you start making spell-like effects that are not spells.



2. Detect Magic detects magical auras and other such effects, but does it work on inactive runes that do not activate their magic until certain conditions are met?

Detect Magic should detect it. Unless you include in it an illusion spell that hide its magical nature. Even if the spell is "passive", it is still actively scanning the environment to check for its trigger. If the spell was fully disabled, it could not trigger seen it could not "observe" the trigger.



3. Would Detect Magic indicate that the chair is magical, or the rune drawn onto it? The chair is not imbued with magic. It just has the rune on it.

Your choice about spell design: is the target of the spell a surface or an object? Is the trigger the act of touching the surface, or to sit in the chair (i.e using the chair for its purpose)?
In the former, dispel magic will show the surface, in the later, dispel magic will show the chair.