D&D 5E Tremorsense

[Warmaster Horus]

Tremorsense (from the MM)

A monster with tremorsense can detect and pinpoint the origin of vibrations within a specific radius, provided that monster and the source of the vibrations are in contact with the same ground or substance. Tremorsense can't be used to detect flying or incorporeal creatures.
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One of my PCs was awarded Ironfang, one of the legendary elemental weapons from Princes of the Apocalypse. Among its' abilities is giving its' wielder Tremorsense in a 60' radius. This is turning out to be very handy for detecting hidden enemies even through barriers like walls and closed doors.

I find I'm using it like a motion detector in Aliens. Example...

PC: I approach the door and with Tremorsense active. Do I pick anything up?
DM: Yes, there are five sources of vibrations. Three are clustered 20' to the northwest and two others are 30' to 40' to the northeast.
PC: [whispering to party] "Okay, we've got contacts..."
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Any thoughts as to whether it can determine the extent of rooms, furnishings, hidden spaces, etc? The 'vibrations' of empty space would differ from that of solid, for example. How about other cool ideas for using it in play? Thanks!

 

[Sacrosanct]

It only detects vibrations. So anything that isn't creating vibrations (moving) doesn't set it off. This includes motionless creatures. Think the creatures from the movie Tremors

 

[AaronOfBarbaria]

I'm with [MENTION=15700]Sacrosanct[/MENTION] on this one.

However, if you do want the PC to be able to get a "read" on a room through walls, there is a ring for basically just that (x-ray vision) in the DMG list of magic items.

 

[Warmaster Horus]

I agree with the motionless part. Except that as a DM I would rule that a creature would have to be intentionally being very still, or peacefully asleep, to not be detected. Just standing or sitting in one place would still include lots of 'vibration' like eating, shifting your feet, etc.

 

[Warmaster Horus]

I'm with [MENTION=15700]Sacrosanct[/MENTION] on this one.

However, if you do want the PC to be able to get a "read" on a room through walls, there is a ring for basically just that (x-ray vision) in the DMG list of magic items.

Do you know such a ring in Adventurer's League?

 

[AaronOfBarbaria]

Do you know such a ring in Adventurer's League?

Nope, I don't do go in for having my hands tied as a DM like that.

 

[JackOfAllTirades]

I agree with the motionless part. Except that as a DM I would rule that a creature would have to be intentionally being very still, or peacefully asleep, to not be detected. Just standing or sitting in one place would still include lots of 'vibration' like eating, shifting your feet, etc.

Does "peacefully asleep" not include snoring really loud? Tremorsense might notice that.

Then again, so would anyone with decent hearing....

 

[Warmaster Horus]

Does "peacefully asleep" not include snoring really loud? Tremorsense might notice that.

Then again, so would anyone with decent hearing....

Actually, going over the definition again, it includes the statement that flying and incorporeal creatures cannot be seen by Tremorsense. Given this, I would make it very hard for corporeal, living beings to hide from this sense.

 

[Nifft]

IMHO anyone moving would get pinpointed.

That includes rolling over in your sleep, but not merely breathing.

Monsters in hammocks would be immune to detection, because hammocks are awesome.

 

[Ovinomancer]

IMHO anyone moving would get pinpointed.

That includes rolling over in your sleep, but not merely breathing.

Monsters in hammocks would be immune to detection, because hammocks are awesome.

Well, to get to modern technology, I've actually had my hands on something that could easily detect breathing on the far side of a fairly think wall using microwaves. The act of the chest wall moving is enough. In that sense, I'd allow tremorsense to detect anything corporeal and in contact with the ground so long at no active effort to evade detection was underway. Makes things easier and less of a gotcha! (you didn't know the dragon was there because it was just breathing, roll for initiative!)