Curse of Strahd
Any one poison can only have its DC increased by your proficiency once unless the effect states otherwise. Any damage bonuses to poisons that last longer than one turn is half the proficiency bonus and -2 if it last longer than 3 turns. Furthermore any one potion may only be infused with a single essence. If more than one is used the brew is inert.
Chart for Roll vs. Rarity
1: Finds a flower that will instead cause healing
2-5: Fails to find anything of use
6-10: Gives common materials only usable as a base poison ( C )
11-15: Gives uncommon materials (Un)
16-20: Gives rare materials ( R )
21-25: Gives super rare materials (SR)
Legendary Materials: Gathered only when you kill the correct enemy and succeed on gathering the materials. (L)
Unique: Like legendary materials these can only be gathered from the corresponding enemy (U)
• To craft a single poison one must take care to very carefully and painstakingly craft it. It takes one day (assuming you have the materials) to craft any one poison.
• An Alchemist must be very careful when selecting ingredients and therefore to gather the materials for any one potion takes either 1 hour per ingredient if it is your only task or one day of travel for 3.
• Any one potion can only have 2 secondary ingredients. The DC to make a potion with two secondary ingredients is +5 for Uncommon and Rare ingredients +10 for SR ingredients.
For the Word Document with known ingredients you can find those here.