>Perhaps the devil saves you from an intro fight before you make your pact?
Indeed, there will be a new intro in the next release.
>I hope this isn’t a one time tutorial thing and is actually introducing me to a mechanic that is used throughout the game.
You are correct.
>It wasn’t clear to me how to cure the poison?
Antidote is an unlockable recipe. But in general, the best tactic is not to get poisoned, or at least not let it stack too high.
Vipers aren't actively aggressive, but I know a lot of people have issues with them.