Does Detect Magic always detect Alarm spells?

[Captain Morgan]

Alarm isn't illusion, so it didn't have the old "immune to lower level detect magic" clause and is an awfully small spell to be heightening anyway. But if PCs can auto spot it with detect magic and then dispel it, it isn't a great alarm system.

Can you use some other spells to cloak it, like Misdirection?

[Sibelius Eos Owm]

I want to note 'spot it with detect magic' isn't actually possible until like character level 7. If they approach a warded area with detect magic, they will know that there is magic but not have any leads on what, without further investigation. They likely would need to start Seeking and/or Recalling Knowledge in order to figure out where/what the magic effect detected was before they could even Dispel it, during which time they may still accidentally misstep and trip the spell

[thenobledrake]

As Sibelius has noted, detect magic is not going to directly foil an alarm spell.

The caster detecting magic is only going to get "yes, there is magic you didn't know about with 30 feet of you" from the spell, and will likely stumble into the alarm spell while looking for things to use read aura on to figure out what the magic actually is.

The caster won't even know "there's abjuration magic nearby" from detect magic until 5th level, and even then they won't know it's an alarm spell rather than some other kind of abjuration because there are a lot of things which would give the same indicator.

Even once the caster is 7th level or higher, detect magic will just point them in the right direction to start trying to figure out if they are looking at an abjuration spell in the 5-foot cube indicated or, as an example, an invisible ring of energy resistance.

And in any case, the caster has to deliberately not enter the area of the alarm while figuring out what it is and spend however long it takes for them to Identify Magic on the effect to figure out it's an alarm spell.

At which point they can finally try to dispel it.

But yes, I believe you can use spells like magic aura and misdirection on the thing you touch when casting an alarm spell to add another layer of difficulty/delay to this.

[mrspaghetti]

Think of it like using a thermometer to take your temperature. It tells you if you have a fever, but not why. Could be any of billions of microbes, or something else entirely.

[Captain Morgan]

The thing is, by level 11 once you get a ping on Detect Magic you can stop and Read Aura on every object within 30 feet. Once you identify where the magic is coming from, you can ID it. I'm also not sure you can use Magic Aura or Mislead on Alarm, because those work on objects and Alarm doesn't target an object.

The best use of it I can think of is to cast the Alarm close enough to where you can hear someone casting and searching around for it. I've got a 17th level caster spy type and I'm trying to think through what tactics he can use to not get ambushed.

[Brutedude]

How high level are these PCs? The rules for Dispel Magic are you need to beat the caster's DC. For a 17th level caster who maxed out their casting stat that would be 40! If the players can't beat the Alarm they're going to alert the villain even if they know it's there.

If your players are high enough level that they can reasonably expect to beat a DC that high or slightly lower, well what would your villain do? They'd have to know that the only way someone can enter without alerting them would be if they were comparable to themselves in magical ability. I imagining some kind of a death trap that the villain has set up that would only go off if someone managed to enter while bypassing the alarm.

[Moppy]

You kow there is an alarm on a wizards tower anyway, and there's so much magic there I doubt you could locate the individual spell.

In some cases like a wilderness camp, not using magic might make it harder to locate the camp, since detect magic will reveal it.