The glyph created by the spell glyph of warding is hard to see:
The glyph is nearly Invisible and requires a successful Intelligence (Investigation) check against your spell save DC to be found.
If the glyph is in an area of dim light or light obscuration, is the check made with disadvantage?
Perception checks are usually made with disadvantage in such conditions, but it's not clear to me if it also would apply to the investigation check to find the glyph.
The rules for dim light and lightly obscured do not mention investigation:
In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight.
But, the rules for advantage and disadvantage say:
The DM can also decide that circumstances influence a roll in one direction or the other and grant advantage or impose disadvantage as a result.
So the DM May certainly rule that the check should be made at disadvantage if they think the environment warrants that.
There’s nothing written in the rules that explicitly tells you the check would be at disadvantage in a lightly obscured environment. It’s totally up to the DM.
Notably, heavily obscured imposes the blinded condition:
A heavily obscured area--such as darkness, opaque fog, or dense foliage--blocks vision entirely. A creature effectively suffers from the blinded condition when trying to see something in that area.
Blinded says:
- A blinded creature can't see and automatically fails any ability check that requires sight.
Since a heavily obscured area (such as total darkness) would definitely make it impossible to see the glyph, it seems quite reasonable that a lightly obscured area, such as dim light would make it more difficult to see the glyph and impose disadvantage on the investigation check.
