D&D 5E Detect Magic and hidden (unseen) objects

[Chaosmancer]

I've never heard of any DM going down the path of "the answer eventually becomes..." That's the absurd part I'm talking about. The spell doesn't become stupid the instant your party gains its first magic item.

Maybe I've misunderstood your point, reading back through the posts it does seem like you allow the caster to know there is a magical item in the sack.

So, do you allow them to know if there is a magical item hidden behind a brick a fireplace? The spell penetrates a foot of stone and I've never seen a brick thicker than that.

How about if there is an item in the next room? Most wooden walls I've seen would not be three feet thick, so the spell would penetrate that as well.

So, this is the problem in my understanding. You say the spell is "not an auto-finder" but it is specifically written to pierce through barriers. So does the spell tell you that there is a magical item in the wardrobe, past a few inches of wood, or does it simply say "hey there is magic in this room".

And if it is the second, how can you ever tell if you are detecting yourself, or something else, because if you don't get some directionality and specificity, then I don't see how the spell wouldn't be "stupid" and be rendered blind by your own magical items.

 

[Enevhar Aldarion]

And if it is the second, how can you ever tell if you are detecting yourself, or something else, because if you don't get some directionality and specificity, then I don't see how the spell wouldn't be "stupid" and be rendered blind by your own magical items.

The spell has a Range of Self, which means either the caster is the originating point of the spell, but not in the spell's effect, or that the caster is the only target of the spell. And Detect Magic is definitely the first, so nothing on the caster will show up for the spell.

But even if you do not want to run it that way and assume anything on the caster triggers the spell, then the caster just automatically moves to the second step and makes anything else magical within 30 feet give off that faint aura. And emphasis on faint, as the faint auras around the caster's magical items are not going to blind him from seeing the other faint aura that something 29 feet away is giving off.

Now, the other party members triggering it is another thing. They would have to back out of the 30 foot range first, so that the caster could tell what around was magical.

 

[Chaosmancer]

The spell has a Range of Self, which means either the caster is the originating point of the spell, but not in the spell's effect, or that the caster is the only target of the spell. And Detect Magic is definitely the first, so nothing on the caster will show up for the spell.

But even if you do not want to run it that way and assume anything on the caster triggers the spell, then the caster just automatically moves to the second step and makes anything else magical within 30 feet give off that faint aura. And emphasis on faint, as the faint auras around the caster's magical items are not going to blind him from seeing the other faint aura that something 29 feet away is giving off.

Now, the other party members triggering it is another thing. They would have to back out of the 30 foot range first, so that the caster could tell what around was magical.

See, that leads to the "stupid spell" problem.

You cast detect magic. To tell if there is magic in the room (because the aura is only for determining the type of magic) you need all your friends more than 30 ft away. You need to have your familiar out of the room (it is a magic construct after all). Then after you find one item, you need to set it more than 30 ft away, because it might not be the only thing, and it is interfering with the spell.

And if you happen to be inside a magical fortress? Well, detect magic is useless. Because it registers the fortress and nothing else.

The magical trap at the exit to the room? Blocks out you finding any other magical items in the room.

And on and on.

I find it much more reasonable that the spell says "hey, there is a little magic to the left, and then a big splotch of magic under the floor to the right, and something magical under the bed." Because then it is actually useful.

 

[jgsugden]

You cast this spell. It requires either an action, or 10 minutes plus an action as a ritual. At the time you cast the spell, you can sense whether there is magic within 30 feet of you. If the source of magic is separated from you by 3 feet of wood, 1 foot of stone, 1 inch of common metal, or a thin sheet of lead, the spell will not detect the magic.

Detect and sense are ambiguous terms in 5E that are not defined. As such, we turn to a dictionary and get a definition of "a feeling that something is the case". As a result, this first initial blush of the spell is a binary toggle that turns on if there is any magic within 30 feet of you. You continue to sense magic in this way and would become aware if magic enters your 30 feet visible radius (or a barrier is removed) while you concentrate. However, if there is already magic in the area, your binary detection of magic does not change when a new magic source enters the area. Some people call this a "stupid spell" problem because most PCs walk around with some magic on them. The spell does not exist solely for PCs. Most low level clerics and wizards that can cast this magic may not have any magic items.

Note that per sage advice, constructs animated by magic do not detect as magic by themselves. They were given the spark of life by magic, but are no longer magical. It would seem the same is true of undead from an instantaneous source (like a zombie from a finger of death or a wight), but not of summoned or animated undead with a duration.

If you detect any magic, you may then use another action, so long as you are still concentrating on the spell, to look for magic auras. A 1.) visible 2.) creature or object will show you a faint aura that reveals the school of magic, if any.

Visible is not inherently defined either, but there are a few elements in the rules that clarify when something cannot be seen. Invisible and heavily obscured (including those shrouded in darkness) creatures or objects cannot be seen. If a creature is successful in their attempt to hide, they gain the benefits of being an unseen attacker/target. As such, a hidden creature concealed by stealth is presumably unseen, and thus would not detect as magical (assuming perception is not greater than stealth). Similarly, an object that has been concealed with sleight of hand should also be unseen as well (unless perception beats sleight of hand).

Absent a sleight of hand or stealth role to conceal the object or creature, non-skill based techniques can be used to obscure the creature or target so that no aura is detected. Any barrier that prevents direct line of sight to every part of the creature or object would prevent an aura from being generated. If, after the magic is applied, the entire object were painted, or covered in a thick layer of flour, or put into darkness it would not emit an aura when the second element of detect magic is used.

"But it glows! How can darkness hide something that glows?" you might ask.

It doesn't glow. It doesn't do anything unless it is visible. In this chicken and the egg scenario, you need to see the object or creature before it can emit that faint aura. If you do not see it, it does not glow.

Also, illusions and other spell effects are not creatures or objects, generally. Accordingly, a light spell cast on a stone would emit an aura because the stone is an enchanted object, but a dancing lights spell would not. They'd both trigger the initial "sense" that magic is present, but dancing lights would not emit a magical aura when that extra action is used to look for auras.

 

[TaranTheWanderer]

It doesn't cause things to glow. It targets the caster, enabling them to see the subtle auras that surround objects and creatures. You, therefore, have to see the object unobstructed to see the aura. The colour of the aura is how you identify what kind of magic it is.

I usually hand waive it by saying, "you sense magic in the room." but leave it to mundane methods to search for an item, if it's not in plain sight. My reasoning is that the caster is used to the 'feel' of whatever magic items are usually around him/her. Just like people get used to their own smell, regardless of how bad it might be. It's the presence of a 'new' energy within 30 feet causes his senses to tingle.

And, yes, in a magical tower, the omnipresent feeling of powerful magic might prevent you from noticing more subtle magics...like how a powerful smell can mask more subtle ones. (think skunk) Especially things like artifacts. I might allow a skill check or, just time, to be able to try to tune out the auras that are blocking others. But that's a complication of the scene/game you're running. You're doing an adventure in a magical tower, so there are side-effects that you need to overcome.

In any case, I don't like allowing detect magic to be an auto-find spell but I do like giving enough room to allow it to give characters a reason to do a more thorough search.