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I'm running a game and my players entered a room which was under the effect of a Mirage Arcana spell to make the room look nice. One of the players cast detect magic. Does this reveal the illusions?

I'm wondering because I can't justify a 0th-level spell overcoming all illusions. Does illusion magic have any built-in protection from detect magic (true sight and arcane sight are not being asked about)? Also, I am not asking about invisibility, but disguise magic should also be included.

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Fering
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  • Don't forget that even without magic, the players get a saving throw if they interact with the illusion (ie; as soon as they enter the room). Having a spell that is specifically designed to detect things like this detect them isn't all that strange. – Erik Sep 14 '15 at 11:00
  • Detect magic isnt specifically for illusions. There was some debate over what interaction meant as well. Did just seeing the illusion count or was there more to it than just that? – Fering Sep 14 '15 at 12:46
  • @Fering You could ask that as a question, but you might not need to after checking a dictionary. (“Interact” means both entities affecting each other, which doesn't happen with an illusion just by looking at it.) – SevenSidedDie Sep 14 '15 at 18:32

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Detect magic would reveal the presence of magic, in most cases, but not the exact illusion being used.

Concentrating long enough with detect magic would indeed reveal that magic of the illusion school had been used, and what area it covered. However, it wouldn't automatically grant knowledge of what had been changed to look like what. So now they know that the appearance of the room has changed, but they don't know what it looked like originally - or what you might have covered up with your illusion. Maybe they'll be twice as wary because they think the illusion is hiding traps or monsters, when its actually just making the place pretty.

Note that illusionists have ways to hide their magic as well - magic aura, mask dweomer, and misdirection come immediately to mind, but there might be ways to hide or change an entire room's aura as well at higher levels.

gatherer818
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  • Just knowing that the room is blanketed by magic pretty much gives away that its an illusion spell. I know about magic aura but mask dweomer is something I did not know about. But this encounter didnt have any means to protect the illusion. I guess this will have to be a house rule. Thanks for clarifying it for me. – Fering Sep 14 '15 at 00:56
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    @Fering you might try having a stronger aura over the illusion, if it's actually important to hide it. The important part though is still that while they might know it's an illusion, they don't know what parts of what they're seeing are illusions, and what they actually look like. Spells like sanctuary or guards and wards can cover areas with abjurative magics, or even a sanctification against undead could give a necromantic aura that overpowers the illusion aura. – gatherer818 Sep 14 '15 at 01:07
  • Wouldnt the overlapping of auras only work for the first round. The second round tells you the number of auras – Fering Sep 14 '15 at 01:30
  • @Fering There's also a line that says that particularly strong or numerous auras can hide other auras, but there's little guidance for the GM about how much aura is enough for this to happen. – GMJoe Sep 14 '15 at 01:33
  • @Fering you're mostly right, I was thinking of something else. However, it would still take until round three, when you learn where each aura is and can start identifying each aura's school with Knowledge(arcana) checks. – gatherer818 Sep 14 '15 at 01:33
  • As the DM, if you really need it to be hidden, you could of course Rule Zero it, but I'd probably justify that somehow with a nearby wizard with a few scrolls of [Wizard's Name]'s Area Misdirection and some spell research notes or something. – gatherer818 Sep 14 '15 at 01:37
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To expand upon the above answer, this is also a common trope. Think of the times in stories where a sage has said: "You are not who you appear. Show me your true face!" Or "hmm, this wall is projecting an unusual aura. Something isn't right here." As a DM you can share the results of a successful Detect Magic as such, revealing that the illusion seems off, that there is a magic aura, without saying the item or person or sound is in reality an illusion.

Knowing most players, they will first suspect a trap or a hidden escape, or that something valuable is there. Your illusion should be reasonably safe for a while.

Fnordius
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    You should not 'expand on previous answers'. all answers should stand alone. – Tritium21 Sep 14 '15 at 10:45
  • @Tritium21 While this is technically true, I see it done all the time. "While X answered this question very well, I have something I'd like to add..." – Jason_c_o Sep 14 '15 at 11:11
  • @Jason_c_o I will quote my mother here.... "If all your friends jumped off a bridge..." .... which I have a tangential answer for, but you get the point. – Tritium21 Sep 14 '15 at 11:13
  • @Tritium21, apologies for my late answer, as I didn't think to check for replies. You may want to quibble with the way karma lets new users add their own "answers" but not "expand", as you put it. – Fnordius Oct 14 '15 at 12:12