Detect Magic, Illusions and invisibility

[MrOrange98]

My players are trying to convince me that the mage with permenant detect magic can see through illusions and invisibility. I say no because there are spells like see invisibility and true seeing that would be replaced by a 0 level spell. Can I hear arguments and references either way.

Thanks

 

[Murrdox]

Wow.

Even though Detect Magic is a level 0 spell, it is a really powerful one, especially if it is permanently on a subject, basically making it a Supernatural Ability.

A creature with Invisibility cast on it WILL indeed give off a magical aura that will be detected by the character. However, he will have to concentrate for 3 rounds before he can pinpoint the exact location of the invisible creature. Of course, this also means that if the invisible creature moves out of the arc of the detect magic ability (for example, moves behind the caster) he may have to start over again if he doesn't move the arc to cover the invisible creature again.

The same thing goes for illusions. For example, let's assume that the character in question runs into a Permanent Image of a sleeping dragon.

Before the character is within 60' (range of the spell) all he sees is a sleeping dragon, and he will assume it's real unless he does something to interact with the image beyond this range.

Once he gets in range of the detect magic, he will sense a magical aura. The next ROUND, he will sense the number of auras, and their relative strength. In this case, he'd sense ONE aura, of sufficient strength to be a Permanent Image spell. On the third round, he would know that the magical aura that he is detecting is coming from the dragon. At this point he can ALSO make a spellcraft check at 15 + spell level to figure out what school of magic is involved. If he sucessfully made this check, he'd know that this dragon has an illusion spell cast on it.

Now, this doesn't mean he KNOWS the dragon is an illusion, but he knows there's some type of illusion on the dragon, and he knows how powerful the illusion is. From this information, he may be able to deduce that the dragon is a Permanent Image spell, or at least that there is an illusion spell cast on this dragon with the same spell level as Permanent Image.

If he fails to identify the school of magic, all he knows is that the dragon is radiating a magic aura... what it is could be anything.

 

[Bauglir]

Using detect magic, a caster can indeed see invisible creatures and illusions as magical....


after staring for 3 rounds.

The character detect magical auras. The amount of information revealed depends on how long the character studies a particular area or subject:

1st Round: Presence or absence of magical auras.

2nd Round: Number of different magical auras and the strength of the strongest aura.

3rd Round: The strength and location of each aura. If the items or creatures bearing the auras are in line of sight, the character can make Spellcraft skill checks to determine the school of magic involved in each. (Make one check per aura; DC 15 + spell level, or 15 + half caster level for a nonspell effect.)

So in the case of an invisible foe, the magic detecting caster has to first know that he is in the area, (Note that the caster is surrounded by adventurers, most likely dripping with magic items, so the 'Presence or absence of magical auras' will not pick up the new aura) and his rough location (detect magic working in a 60 degree arc), then concentrate on that area for 3 rounds. If he moves out of the arc, the caster must start all over again with the concentration.

 

[Kershek]

If I remember correctly, the FAQ states that if the target moves at all you have to start over with your concentration.

 

[AuraSeer]

If I remember correctly, the FAQ states that if the target moves at all you have to start over with your concentration.

Nope, read it again. The detection works as long as the target is within the detect cone on the three consecutive rounds.

 

[Black Omega]

Permanant Detect Magic can be pretty cool for a wizard. The illusionist in the game I run has it and it's been fun to work in now and then ways to use it.

Generally, he detects magic but not type and place. We've been doing it so that unless that invisible target stands still, he can't pinpoint them and it's worked well.

 

[Norfleet]

Well, detect magic has a rated range of about 60 feet. It detects in a "quarter circle", which would be a 90-degree arc, meaning a 45-degree angle from the center line. The area of this construct is therefore of 0.25*PI*60^2 = 2827 ft^2.

Using this for invisibility scanning, a blip indicates your invisible opponent is somewhere within this area.

Webs and Fireballs have a 20-foot radius of effect, by default, and a range which easily allows you to target any point within this arc.

These, therefore have an area of effect, therefore, of PI*20^2 = 1256 ft^2.

A rough glance suggests that most, say, about 90% of this will be able to fit within the pinged area, so you have a coverage on the order of 1100 ft^2. With just wild guessing, you have therefore a 1100/2827, or about 40% chance, of hitting your target just guessing wildly. A more educated guess can easily improve this, such as figuring that a newly detected target has just entered the area, and will therefore be on the outer edge, or the sweep line, depending on your search pattern.

This chance becomes much greater if there's a metamagic feat you have which can enlarge the area of effect even slightly, or if a more suitable coverage spell than the ones that come to mind above can be used instead.

FIRE IN THE HOLE!

Hey, beats waiting 3 rounds.

 

[Black Omega]

Not a bad idea, but....

That will only work if there is no one else in the area with any magic. If you big tough fighter with the magic plate armor and +2 great sword is in the area as well, then all you know is there is magic in there. You won't know where and what the magic is until the third round.

Now if you are alone, that tactic works much better, though then the wizard has a whole host of other problems.

 

[Stalker0]

As for teh illusions, after 3 rounds if you know an illusion spell is "on" the dragon, I would then give a will save for the illusion (and not before). Fail it, and your just not sure what's real and what's not.