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Suppose there is a device in the middle of a large but ordinary room that creates a permanent anti-magic field with a 10-foot radius (as per the Antimagic Field spell). A spellcaster suspects that the device is magical, so she casts Detect Magic (60 foot range, cone-shape) while standing 30 feet away.

Would the spellcaster detect the presence of the antimagic field, and does it depend on whether the field is from a magical item vs. cast by a spellcaster?

We know that the Detect Magic spell gets cast successfully because the caster is outside of the antimagic field. Presumably, whether or not the antimagic field gets detected depends on whether or not the antimagic field has an aura that extends past its radius. If the device had a 1 foot magical aura, then the Detect Magic spell would presumably not be able to detect the tiny aura because it couldn't penetrate into the antimagic field.

Another question is whether a magical aura is itself suppressed by an antimagic field, and whether an antimagic field itself produces any aura.

Note: this other question is extremely relevant, but does not discuss my particular question: Do you know that Detect Magic is being suppressed if it intersects with Antimagic Field?

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  • \$\begingroup\$ So I don't know if this helps but another way to think about is; does detect magic detect an aura of magic or just the device that creates it? \$\endgroup\$ – Jared Kossler Jan 25 '17 at 0:28
  • \$\begingroup\$ As far as I know, Detect Magic detects auras of magic. A magical item would have at least one magical aura emanating from it, which Detect Magic would let a caster "see" or "sense". \$\endgroup\$ – jvriesem Jan 25 '17 at 4:43
  • \$\begingroup\$ @JaredKossler jvriesem is correct, you never detect the device, you are always detecting the magic aura created by them (hence the description on each item about the strength of is aura from faint to overwhelming) \$\endgroup\$ – Ifusaso Jan 25 '17 at 5:01
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Detect Magic would sense a Moderate or Strong Abjuration aura when looking at the Antimagic Field(AMF), but nothing within the field.

Despite being a sphere of antimagic, AMF is still a spell effect and produces an aura as anything would. Per Detect Magic, a 6th level spell would produce a Moderate aura, and its 8th level version produces a Strong aura.

Detect Magic's stated target is an area 60ft long, not a personal spell. Any range that extends within the AMF would be nullified. They would be unable to determine the source of the aura, unless they could see enough of the sphere to determine its center.

A further note, except in cases of GM Fiat, AMF will be centered on a creature. The spell states "An invisible barrier surrounds you and moves with you." Furthermore, there is no RAW item that has maintains an AMF, and the closest, the +1 Tower Shield Equalizer values the once per day use of AMF for 10 minutes at over 100,000g.

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  • \$\begingroup\$ Just to clarify: the caster would detect an aura coming from the general area of the sphere, but wouldn't necessarily know where within that general area it was originating from, correct? \$\endgroup\$ – jvriesem Jan 25 '17 at 17:14
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    \$\begingroup\$ @jvriesem correct. Essentially looking at it, they would see a mundane area with a 10ft radius sphere of magic around it. They would be able to identify that it's Abjuration, and possibly with a Knowledge (arcana) checks that its AMF but they wouldn't be able to tell the source. However, if they can see enough of it, they could approximate the center (what it's radiating from). If not, then it would take trial and error... ie use a spell, walk until it goes away, then comes back. Do the same the other direction. Look in the center square. \$\endgroup\$ – Ifusaso Jan 25 '17 at 18:00
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    \$\begingroup\$ For the record, I highly recommend against giving an adventuring party an item that creates AMF. It's an inanely powerful ability to have access to for free. It might be best to have the spell GM Fiat'ed as an effect on a room (rather than an item), if that makes sense for the campaign. \$\endgroup\$ – Ifusaso Jan 25 '17 at 18:03
  • \$\begingroup\$ No worries about giving them an item. I basically did GM fiat the effect on the room. It made perfect sense. My player asked a question about this, but then my thinking got academic. :-) \$\endgroup\$ – jvriesem Jan 25 '17 at 19:52
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Would the spellcaster detect the presence of the antimagic field? Yes

An antimagic field is composed of two parts: "An invisible barrier surrounds you", and "the within this barrier". The barrier is an Abjuration effect that would be visible to a spell like detect magic. The field does not suppress its own aura because the effect antimagic field produces is the barrier, and the barrier can't be inside the area it defines.

Does it depend on whether the field is from a magical item vs. cast by a spellcaster? No

The field is an effect; it doesn't matter how it was generated. Perhaps it's a permanent effect of the item; perhaps a permanent effect of the room; perhaps it's temporarily on a spellcaster. The only difference that could apply here is that Artifacts are immune to antimagic field, so if the magic item in the field was an Artifact, you could still detect its aura.


There may be another case I ignored: the room itself produces the field, and a magic item is sitting in the middle. Per the spell description, magic effects are all suppressed and a magic sword would merely be a masterwork sword. Such an item in a field would not produce any magic auras on its own, as it is (temporarily) no longer a magic item.

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  • \$\begingroup\$ "if the magic item in the field was an Artifact, you could still detect its aura" - any source for this? The fact it is unaffected and works does not mean that antimagic field doesn't work as an insulator. For example, thin sheet of lead blocks all auras all right, artifact or not. Now - I don't say you are wrong, I just want to see if you are right. \$\endgroup\$ – Mołot Jan 25 '17 at 8:27
  • \$\begingroup\$ @Mołot No direct source, so I'm open to being corrected. Under the section Magic Item Descriptions, it lists Aura along with things like Price, Weight, Slot, and Description. Description covers the actual effects being suppressed. Auras like this aren't effects per se because they have no effect on anything; it's just a consequence of being a magic item. It's typically suppressed because the item is no longer magic. Since artifacts are still magic, I'd say they still have magic auras. Additionally, the aura is a property of an artifact, and the spell says it doesn't affect them. \$\endgroup\$ – Joel Harmon Jan 25 '17 at 12:41
  • \$\begingroup\$ But how far out does this aura extend? Past the edge of the AMF? AMF states that magic is suppressed within its range, so detect magic would have no effect in the AMF, and hence couldn't sense anything (artifact/god) inside the field. Not because the aura isn't there, but because Detect Magic isn't there. \$\endgroup\$ – Richard Jan 12 at 19:38
  • \$\begingroup\$ @Richard I'm unable to find a reference in the books for exactly how far an aura extends. It's clearly not a "magic items glow brightly to you", because Detect Magic takes 3 rounds (18 seconds) to identify which item(s) are emitting auras. From that and the usual English language definition of 'aura', I can only conclude that auras loosely drop off with distance, and would likely fill the OP's example room. That is, I am presuming the aura itself would extend outside the AMF. I'd be interested in a citation one way or the other, if you have one. \$\endgroup\$ – Joel Harmon Jan 15 at 4:36

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