Harvesting a monster part requires 10 minutes and the proper tools. The most useful organs are the ones that produce the monster's special abilities, such as a dragon's lung (fire breathing) or a dragon's scales (fireproofing). Magical plants can also be harvested, although they usually grow in dangerous or lost locations. Body parts or plants harvested take up at least one slot, due to the packaging and fluids they must be preserved in.
Brewing a potion requires a fire, a cauldron, ingredients, and four hours (one watch) of time. The player describes the effect and duration of the potion they are trying to make, along with the ingredients to be used (usually monster parts, but in theory any rare substances with the right properties could be used). If the GM approves the attempt, the PC makes an INT check. The PC adds +5 to the check if they spend an additional watch brewing. On a success, the potion is created. The parts are lost no matter the outcome. If the PC succeeds at the check by 10 or more, they have created a recipe for that potion and no longer need to make a brewing check to make it when using those exact ingredients.
Potions allow the drinker to produce a single significant magical effect. If the effect is ongoing (like invisibility) it lass for 10 minutes (one turn). Weak ongoing effects may last for an hour or even a day if they are very weak. A drop of a potion gives a clue as to its effects. If the players find or buy a potion you can either use one of the examples to the right or generate something using the magic tables.
Here is a randomly generated potion using the tables in Knave 2nd Edition.
Umber color.
To brew this, you’ll need to harvest the relevant ingredient (monster parts probably) and natron.