So i have seen some people with "poison vials" in their inventory but how do you make them?
I'm pretty sure you're supposed to find out in game, but let me give you a hint:
How do you make health kits?
Pretty much what Quest said here, you are supposed to figure it out by yourself. His hint should help you out narrowing down what you need to do.
anything else?
Nothing else.
Requesting closure.