Such as your character keeps telling you how they’re blind/weakened/frozen/confused/whatever, I had the very simple idea of adding a bunch of coughing / struggle-breathing sounds whenever you enter a poisoned cloud, or perhaps even get poisoned.
It shouldn’t be everlasting, just a warning that you’re standing in something bad. It should NOT be any more or less annoying than the typical I CAN OUTRUN A CENTAUR voice.
I think adding details like this into the game is fundamental for improving it, it’s simple. Just put a bunch of co-workers in front of the mic, get some cinamon and cough your lungs out. I believe it will help the immersion a lot. Even if it doesn’t seem like a lot.