Potion Craft: Alchemist Simulator

You start the game with the recipe for this in the 'legendary recipes' tab but here's the breakdown for how to get it--

First you need to have gotten the first part of the alchemy machine from the alchemist merchant that will come by every now and then between customers.
Next you need to fill in the different beakers with the parts from the recipe.
The first one says you need 3 poison but what this really means is a tier 3 poison potion, which is obtained when you nearly perfectly line up your bottle with the poison potion bottle on the alchemy map. I would suggest the best way to get a tier 3 potion would be to overshoot your bottle past the potion you're trying to get and then use the water ladle to very slowly line it up.
Using the same method, you also need a tier 3 strength potion, a tier 3 potion of stone skin, a tier 3 potion of sleep and finally a tier 3 potion of slowness.

In case you haven't found these potions yet, here are their locations -

Poison - directly south-west from the centre
Strength - directly south from the centre
Stone skin - south from strength, around a small wall of bones
Sleep - if you go directly right you will find frost, and south-east of frost is where sleep will be.
Slowness - south-east from stone skin, must be approached from underneath as the top of it is surrounded by bones.

After filling in the parts of the alchemy machine with the tier 3 potions following the recipes in-game, hold down the lever and you will have nigredo!

Side note: in order to complete the game and get all the cheevos, you are gonna need to make 8 nigredo in total.