UngeheuerLich
Legend
The flour should indeed become invisible. But if you make flour fog, there is now a big hole in it. Still disadvantage to hit, but no way the invisible creature can hide.
On the other hand, a magical lantern that reveals invisible creatures by casting their shadows in visible light would be pretty cool, IMO.
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Pauper
It seems RAI, the covered in flour trick should work:
https://www.sageadvice.eu/2015/10/1...p-an-object-does-the-object-become-invisible/
Still not buying the "lantern" bit, though.
Lantern of Revealing
DMG
Wondrous Item, Minor, Uncommon
2 lbs.
While lit, this hooded lantern burns for 6 hours on 1 pint of oil, shedding bright light in a 30-foot radius and dim light for an additional 30 feet. Invisible creatures and objects are visible as long as they are in the lantern's bright light. You can use an action to lower the hood, reducing the light to dim light in a 5-foot radius.
A regular lantern, no. But this...
Remember though an invisible creature still needs to take the hide action to actually be removed from the map. Invisibility grants the chance to take that hide action, otherwise you still know where the invisible creature is, you just can’t see it.
And yes flour works great. It’s also a great use of something like alchemists fire or acid (you still see the smoke or vapors from the creature or its possessions burning) or a bullseye lantern as it still casts a shadow, see “The Shadow” series.
A creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target's person.