Solved
Robots
How does pathfinder get effected by caustic's nox gas even though he aint got a respiratory system which is confirmed by his famous catchphrase "hold your breath if you have to breathe!" Or "hold you...
This is essentially an assumption, but I'd assume Caustic's gas is a mixture of mustard gas plus some other corrosive substances that would accelerate the rate of rust accumulation. Essentially causing robotic characters softer internal structure to degrade rapidly, thus giving them damage.
