So I have been playing D&D for some while now, since 3.5 (skipped 4e) and crafting in D&D has always been something I detest as its REALLY poorly handled in my opinion as a game designer myself.
I am currently DMing a game and one of my PCs is a rogue who has a poisoners kit and wants to develop poisons to coat his weapons. I can easily homebrew some stuff up if needed. But I was curious if there was anything in RAW (either DMG or PHB) that states what it takes to actually create your own poisons, and what poisons a player can create. Page numbers to support claims is highly preferred. I have looked through the books but was unable to find anything substantial except for the Poisoners Kit which says something along the lines of "Allows the Player to create poisons".
If there are no RAW solutions to this problem I have something in my back pocket for it so that isn't really what I am looking for.
Best Answer
The DMG pp. 257-258 has a bit of what you're looking for: descriptions of fourteen sample poisons, with damages and costs. A few individual descriptions contain enough detail to make (some) ingredients obvious--see Carrion Crawler Mucus and Serpent Venom, for example.
As for crafting poison...
Even combined with the PHB Poisoner's Kit (p.154: "Proficiency with this kit lets you add your proficiency bonus to any ability checks you make to craft or use poisons.") and Crafting (p.187) sections, there's not much here to go on. Combining all three sources could go something like this:
I think that's all the rules have got for you.
And here's my bonus inspiration for GMs that read this far: the bottle of 'wine' I saw at my doctor's office this afternoon...
Yes, that's a bottle of wine with an entire cobra in it. And yes, in the cobra's mouth is a whole scorpion.