Detect Magic and changes over time


Rules Questions

The Exchange RPG Superstar 2010 Top 32

It's maybe more a DM call than a rule question, but I'm interested in how you folks would call it...

If a caster is concentrating on detect magic and has been for at least three rounds, would they see any change instantly or would that need to propogate for another three rounds?

Specific case: In my Way of the Wicked game:
A familiar was keeping lookout with detect magic on the necromancer's shoulder. The cathedral in front of them was surrounded by magic (forbiddance, hallow, consecrate) and so were the movanic devas guarding it (aid, holy aura). One of the devas then used antimagic field.

Would the familiar (or any caster of detect magic) see a 'hole' immediately, or sense a change first and need to focus for three rounds?


I'd make it a perception or spellcraft check. Say a base 20 to notice, bonus for size, penalty for range. Give a +5 bonus per round and repeat the check till they notice. I would roll it myself, I wouldn't give the party a clue till the familiar notices. I'd even do that if it was a player with aura sight up.


The amount of information revealed depends on how long you study a particular area or subject.

This seems to indicate that you would need time to study the changes in the auras. Each time you study a different area you need to spend three rounds to get the full information.

Also don’t forget that a stronger aura can mask a weaker aura.

Magical areas, multiple types of magic, or strong local magical emanations may distort or conceal weaker auras.

The effects of the Anitmagic Field on the other hand would be immediately obvious because it has suppressed all magic within its area. This is a function of the Antimagic Field not detect magic. So in general the changes would take time to notice, but in the case you mention it would not.


Pathfinder Rulebook Subscriber

If the caster has been maintaining concentration on a particular 60' cone for 3+ rounds I'd just give him the information. I have a fairly hard time believe that the casting/effects of a 6-8th level spell within 60 feet that a character is focusing on aren't fairly noticeable without detect magic unless they have minimal/non-existant spellcasting skills.


I'd probably let someone focused on an area to immediately notice changes, but even if I didn't I would be hard pressed justifying them not instantly being aware of the gaping hole of no magic at all.

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