"Despite the speed at which a serpent can bite, death from the venom is excruciatingly slow and painful. While most venomous serpents have anti-coagulants in their bite, exsanguination is not your primary concern. Paralysis is. It would behoove you to have the antivenin on your person for immediate dosing, which would be followed up by a blood-replenishing potion. As for   which   antivenin you will need, being able to identify the species..."