How do invisibility and detect magic interact?

[Grimmy]

My players cast detect magic often and several times they've caught someone invisible in the room by noticing the aura. Am I doing this right? It seems like such an easy way to find out someone is there.

[Noir le Lotus]

Yes you can spot someone invisible with Detect Magic, but you need 3 rounds to locate him exactly, and if the invisible creature moves out of the area of the spell, you must restart from the begining.

So yes it works, but that's far from being the easy way to deal with invisible creatures.

[Ryu Kaijitsu]

otherwise there would be no need for the Detect Invisibility spell, honestly, I would argue that Detect Magic wouldn't work at all, but I don't know if it does by RAW, and according to Noir it does

[Knight Magenta]

It hardly replaces see invisibility. I mean, it takes 3 rounds, requires concentration and only affects a cone. Its basically useless in combat. If your PCs are fighting a murderous fey and forgot to prepare their counter-invisibility spells, then this would at least give them a chance.

[Ryu Kaijitsu]

in that way sure, an invisible character easily notices if someone using detect magic stares at the spot he is standing at, and can move out, but the OP-s version of "/spot I found it!" would make it obsolete

[wraithstrike]

Detect magic allows you to locate the square they are in after 3 rounds of concentration. It does not allow you to "see" them. They also have to remain with the cone for the entire 3 rounds. If they move out of the cone then you have to start over.

[mege]

I've always played it that it's very useful against invisible objects and stationary NPCs. Moving NPCs is at best 'he's that-a-way!' confirming that the invisible creature is still near.

[walter mcwilliams]

One more point, it's not radar. Pc's don't detect him running through the Detect Magic cone lol!

[Ascalaphus]

Also, you know there's something invisible there, but you don't know what it is, and you still get the penalties for fighting something you can't see. It's useful but doesn't win the game.

[Archmage_Atrus]

Also, your invisible NPC is an idiot if he doesn't realize there are people around who can detect the residue of spells.

Remember, too, that detect magic only detects the invisibility spell (and similar spell effects.) It does not actually counter invisibility - which means if the creature is invisible due to other means then it does nothing for the PCs.

[Ryu Kaijitsu]

nope, you see something magical at a location (square, not even pinpointing its form or if its on the floor on in the air) for a moment, something that quickly disappears so it may have been imagination, it is not "oops there is someone hiding"

anyway, best to also use nondetection and be done with this