Quote Originally Posted by Black Jester View Post
However, questions, I hope you can answer:
  1. Are there any good third party sources about potions, alchemy etc. you can recommend? This is more about finding new stuff to add to the game or get inspired by.
  2. How would you handle side effects of potion addiction, or side effects? Are there any good rules about potential side effects or addiction?
  3. When we are talking alchemists, the elephant in the room is black powder, and therefore bombs and firearms (at least very simple ones, I am more interested in medieval handgonnes and those cute throwable bombs with a burning fuse than early modern muskets or even rifles). Have you any experiences/recommendations for using firearms in D&D?
  4. What is the worst thing that could happen?
1) I've played a lot of games with alchemy and addictive substances, but all the best stuff are individual item entries scattered across numerous different games & modules. As far as making things, I'd recommend looking at a real book of recipes or chemistry. The interesting parts, or at least parts easiest to gamify, are resource management (we have X, Y and Z, what do we make of them?), mixing ingredient to find new recipes via trial and error (what happens if we mix X and Y?) and playing logic games with ingredients (given known properties of X and Y, what kind and amount of stuff do we need to make Z?)

2) Two chief ways to do this: one, each potion has its own rules. Amount of consumption required for addiction, amount of time required until withdrawal kicks in and quality of withdrawal symptoms or side effects all vary. Two, all consumption of magic potions adds to a single score such as "magical contamination". Magical contamination is periodically checked and may cause all kinds of effects, some desireable, some not, some permanent, some reversible by consuming another potion.

3) I've had exactly zero problems incorporating explosives and firearms up to early modern period to my D&D-like games. Compared to other weapons, firearms are more damaging / capable of penetrating armor than bows or crossbows, but take longer to reload and are noisier. They are typically fired at the beginning of combat to gain an edge before going into melee. Black powder explosives (etc.) are mundane equivalent to fireball. (Material components for fireball are a spoof on black powder anyway.)

4) The likely worst thing is your players being a bunch of negative nellies who stop using potions without even trying the expanded gameplay because they hate the idea of spending any more effort. The actual worst thing is teaching enough actual chemistry to your players that they build a bomb or something. The difference is that the likely worst thing can happen with any rules change that even slightly inconvenience your players, while the actual worst things take a lot more effort & fidelity than you are likely to put in, plus a particular sort of player too. Negative nellies are a much more common breed than people who are inspired to do radical things by games.