Does the above or similar spells/effects counter the concealment gained from fog/mist/etc.?
Creatures outlined by faerie fire take a -20 penalty on all Stealth checks. Outlined creatures do not benefit from the concealment normally provided by darkness (...), blur, displacement, invisibility, or similar effects.
So is fog a similar effect?
How is fog similar to any of those ?
How is fog similar to any of those ?
It's an effect that provides concealment, as are the others.
I'm going to say no.
Those effects operate off concealing or otherwise obfuscating their recipient, who by virtue of just being outlined (or in a lit room) would be easy to spot - whereas fog creates an effect that you can't see through (its not them hiding, its you cant see), even if they were lit up like an xmas tree.
The fog concealment isn't dependent on directly affecting the faery fire'd character,
fog blocks sight past adjacent squares, even to see creatures in full daylight outside of the fog area.
You don't care what effects the target has on it, you aren't seeing anything past the fog.
faery fire affects the targetted creature and other effects on the creature as mentioned,
it doesn't extend to affected fog in unrelated squares, or even in the same square as creature.
THAT SAID, by RAW the creature does take -20 penalty to Stealth, which doesn't care about 'sensory modality', so Perception checks to detect/locate them would be much easier, but would never grant Line of Sight (you would be using sound or other senses).