The Alarm spell in the PHB reads as follows:

You set an alarm against unwanted intrusion. Choose a door, a window, or an area within range that is no larger than a 20-foot cube. Until the spell ends, an alarm alerts you whenever a Tiny or larger creature touches or enters the warded area. When you cast the spell, you can designate creatures that won't set off the alarm. You also choose whether the alarm is mental or audible. A mental alarm alerts you with a ping in your mind if you are within 1 mile of the warded area. This ping awakens you if you are sleeping. An audible alarm produces the sound of a hand bell for 10 seconds within 60 feet

Are there any examples in officially published modules or rulings, errata etc. that indicate whether the alarm spell is visible via a Perception check vs the spells DC or whether the spell is invisible and must be detected through a spell such as Detect Magic or Find Traps?

  • \$\begingroup\$ Something that might jog the memory of someone; I am sure I have read a published module where there is a bell on a stool near an alarm spell, and it specifically says that the bell is the component of the spell and gives a DC to notice this before the alarm triggers. I did think it was death house, but have read through and can't find it, so I am not sure where it is from. If anyone knows they may be able to post that as an answer. \$\endgroup\$
    – SeriousBri
    Feb 8 at 12:31
  • \$\begingroup\$ @SeriousBri A tiny bell was the arcane focus (i.e. the material component) for the Alarm spell in 3.x DnD. \$\endgroup\$
    – Eddymage
    Feb 8 at 13:20
  • \$\begingroup\$ @Eddymage It is the same component in 5e, but the way I remember it is that once the bell is seen (in this mystery module) there is some non-magic way to detect the alarm spell, possibly with a DC of some kind. Even if it was just an arcana check to link bell with alarm it would answer the 'officially published module' part of the question. I just can't find it so hoping more eyes might help. \$\endgroup\$
    – SeriousBri
    Feb 8 at 13:40
  • \$\begingroup\$ Yep, you're right! This "mistery module" belongs to 5e or to a previous one? I can only speculate, but from your description it seems that an inattentive caster forgot the bell after the casting, and then the players have a chance to recognize an Alarm cast on door or area. Let's hope that someone finds out this module! It does not ring a bell to me... \$\endgroup\$
    – Eddymage
    Feb 8 at 13:45
  • 1
    \$\begingroup\$ I was about to accept the answer to complete the question, but I'll hold for another 24 hours unless someone can answer the above. Otherwise the answer given is well reasoned and supported \$\endgroup\$
    – Falconer
    Feb 8 at 23:13

Skill checks are of no use, otherwise the description would have specified it.

By description, Alarm does not leave any visible or invisible sign on the window or the door it has been cast on. If it required a Perception check (or a similar one), the description would have stated so, as it happens for example for Spike Growth (emphasis mine):

[...] Any creature that can't see the area at the time the spell is cast must make a Wisdom (Perception) check against your spell save DC to recognize the terrain as hazardous before entering it.

Another example is Glyph of Warding (emphasis mine):

[...] The glyph is nearly invisible and requires a successful Intelligence (Investigation) check against your spell save DC to be found.


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