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The spell arcane sight is like the spell detect magic only more powerful in that the caster can detect the magic auras right now instead of needing to focus.

And, like detect magic, arcane sight allows seeing a lingering aura:

A magical aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a magic item). If detect magic is cast and directed at such a location, the spell indicates an aura strength of dim (even weaker than a faint aura). How long the aura lingers at this dim level depends on its original power: [Faint 1d6 rounds, Moderate 1d6 minutes, Strong 1d6x10 minutes, and Overwhelming 1d6 days.]

Is it possible to follow an active spell or a magic item by its lingering aura? Or can a lingering aura only be detected at the specific location where the spell was cast or where the magic item was destroyed?

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  • \$\begingroup\$ So in other words, you want to know if you can see the path an invisible wizard took by casting 'detect magic'? \$\endgroup\$ – GMJoe Sep 15 '16 at 5:56
  • \$\begingroup\$ Or just trying to follow someone in a maze, but that works too \$\endgroup\$ – Fering Sep 15 '16 at 6:55
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No.

The spell would need to affect the area around the caster for that to leave an aura behind, or they would need to cast spells wherever they passed. What you want seems more in the realms of ranger spells, or even inquisitor spells.

The lingering aura of a Fireball could be detected on the area, but not spells that were cast on the caster, or on another person. Unless those are the targets being analized. Or if the caster did cast something like Trail of the Rose, that affects an area where the caster passes.

If the spell effect has a Duration, it can be detected as long as the spell lasts. But if the spell effect was Instantaneous, it's Lingering Aura would last only for a short duration, and could be seen with Detect Magic.

Lingering Aura: A magical aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a magic item). If detect magic is cast and directed at such a location, the spell indicates an aura strength of dim (even weaker than a faint aura). How long the aura lingers at this dim level depends on its original power:

Faint 1d6 rounds

Moderate 1d6 minutes

Strong 1d6x10 minutes

Overwhelming 1d6 days

Invisibility, being a 2nd level spell, would generate a Faint Aura, and lasts only for 1d6 rounds after being dissipated.

But Greater Invisibility, a 4th level spell, would last for 1d6 minutes.

A petrification effect would depend on what caused this effect, most creatures's supernatural petrification works like Flesh to Stone, which is a 6th level spell, but has an Instantaneous duration, thus it's aura would last only for 1d6 rounds as a Moderate Aura.

  • Cockatrice: as Flesh to Stone;
  • Basilisk: as Flesh to Stone;
  • Medusa: Does not say, which means it can be detected as a magical aura (being a supernatural ability), but you cannot detect the strength of this aura or identify it. And it most likely does not leave a Lingering Aura behind.

That is, if the creature had no magical items on her, and no spell with a duration. Otherwise, their auras can be detected normally with detect magic or arcane sight. You will see that nothing on Stone to Flesh states that the auras disapear or go inert, which means they are all active regardless of the state of their target.

If a 10th level mage was petrified with Mage Armor (1 hour/level duration) cast on him, his aura could be detected for 10 hours, plus 1d6 rounds.

Similarly, if he had a Cloak of Resistance +1, anyone would detect that as a weak transmuration aura.

There are better options to find someone you want to follow using magic though, such as the spell Locate Creature.

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    \$\begingroup\$ I think I'd note here that spells like Antimagic field that provide an area effect that moves with the target would leave a trail, but they're fairly limited and unique in that. \$\endgroup\$ – Cyberspark Sep 15 '16 at 14:16
  • \$\begingroup\$ @Cyberspark Why would emanations differ from any other mobile spell in this respect? \$\endgroup\$ – topquark Sep 16 '16 at 14:22
  • \$\begingroup\$ @topquark the difference is that the area affects the zone, which would include the ground and objects and items that do not leave along with the zone. Unlike most other mobile spells it affects more than just the target. Most other mobile effects are single-target or multi-target, effecting specific targets which you would need to see and wouldn't leave an aura except for on the target itself. \$\endgroup\$ – Cyberspark Sep 20 '16 at 14:20
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Only dissipated spells and destroyed magic items leave lingering auras

For a source to leave a lingering magic aura, the source must first cease to exist (otherwise the aura's not a lingering aura—it's current aura is either just present or absent). Like the spell detect magic says, "A magical aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a magic item)." If the magic spell is ongoing or the magic item still exists, no lingering aura is present at all.

I think one reason for such a fiddly process may be to allow a creature that's being chased by pursuers that're employing detect magic to discern its ongoing auras an opportunity to escape by eliminating its auras, yet the lingering auras still giving such a creature's pursuers an indication of events surrounding such a creature's escape. This complicated reason likely pales in comparison to informing PCs exactly where that artifact was broken a few days ago, a surprisingly frequent plot point in many published adventures.

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