Detect Magic limits


Rules Questions


Here's one for you guys...The detect Magic spell: "...The spell can penetrate barriers, but 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt blocks it." Suppose a magic item is under water? You are standing on a dungeon floor, and a magic ring, for example, is under 6" of water in a small pool, or font. Does it glow? Say it's 12" deep? 3 feet? What if the water is dirty? Must you stick your head under water to look for magic auras?...


Detect magic isn't a "glow" anymore. Its more of a feeling.

Since it doesn't say that water stops it, it probably doesn't. If you want to equate it to x rays I think you'd need more water than the spells has range to stop it.

Liberty's Edge

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Detect Magic seems to infer that the density of the material indicates whether the spell is blocked. As you said, this is what the book gives us for examples of material that block the spell:
- a thin sheet of lead
- 1 inch of common metal
- 1 foot of stone
- 3 feet of wood or dirt

Without getting too scientific, most wood is less dense than water (although there are a few exceptions). Wood and water are much closer in density than water and stone...so it wound not be a stretch to say that 3 feet of water blocks the spell.


RedDogMT wrote:

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Detect Magic seems to infer that the density of the material indicates whether the spell is blocked. As you said, this is what the book gives us for examples of material that block the spell:
- a thin sheet of lead
- 1 inch of common metal
- 1 foot of stone
- 3 feet of wood or dirt

Without getting too scientific, most wood is less dense than water (although there are a few exceptions). Wood and water are much closer in density than water and stone...so it wound not be a stretch to say that 3 feet of water blocks the spell.

This. Density seems to be the key.


Densities, for some reference (numbers from google searches).

Lead: 11.3 g/cm^3
Iron: 7.87 g/cm^3
Granite: 2.70 g/cm^3
Dirt: 1.92 g/cm^3
Oak: 0.76 g/cm^3
Water: 1.00 g/cm^3

While it does seem linked to density at a glance, there doesn't seem to be the correlation one would expect given their relative densities. Especially telling is the difference between wood and dirt, even though they're mechanically the same.

The rules as written do not say anything about water blocking detect magic, although it is not an unreasonable house rule.

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