You can use 1-4 herbs to make a twyrine extracts - immunity-boost drugs. Your extract will have 2 parameters:
1) + Immunity
2) - Health
In this guide I'll call extracts you get "X/-Y" where X is bonus to Immunity and -Y - health damage
So let's find out how to make best boosts and how expensive they are.

Important notes: The order you add ingredients does not matter, you don't need to follow recipes you found and you don't need to keep recipes items to use them - these thigs are just examples (some are quite good actually), you can make any extracts as soon as you find your equipment (main quest of Day 2).

First, there are 3 types of twyre:
- Bloody twyre, if you make an extract from just this one herb you'll get 6/-6
- Black twyre, if you make an extract from just this one herb you'll get 6/-6
- Brown twyre, if you make an extract from just this one herb you'll get 20/-15

If you put 2-3-4 of the same herb into extract, effects will just sum up. For example extracts from 2xBloody twyre will be 12/-12, 3xBloody twyre will be 18/-18.

If you mix different types of twyre in same extract they can either block each other or work together, in depends on what you are mixing.

1) Immunity bonus: Brown and Black twyre work together, Bloody twyre works against them. So Brown+Black will give you 20+6=26 immunity, Brown+Bloody 20-6=14 immunity, Black+Bloody 6-6=0. It cannot become negative, the 'winner' will always keep his score positive - both 2xBlack+1xBloody and 1xBloody+2xBlack will give you +6.
2) Health damage: Brown twyre works against both Black and Bloody. So Brown+Black will cost you 15-6=9% hp, Brown+Bloody will cost you 15-6=9% hp, Black+Bloody 6+6=12% hp.

Result: The best way to make a perfect twyrine extracts is to combine some Black and Brown twyre. Such extracts will give you very good immunity boosts, and damage to health will be quite small.

Second, there are 2 other herbs:

1) Swevery. If you add 1 Swevery to any twyrine extract, it will double immunity boost, without changing any health damage. Add 2 for x4, and 3 for x8.
2) White Whip. If you add 1 White Whip to any twyrine extract, it will reduce health damage by 2 times, without changing any immunity bonus. Add 2 for x0.25 and 3 for x0.125.

Summary: The best extract should have 1 Brown and 1 Black twyre, at that point it's 26/-9. Now you can either add another Black twyre and then one Swevery, so it will become 32/-3 => 64/-3. Or you can add 2 Swevery for 26/-9 => 100/-9. I find 63/-3 to be the best for immunity boosts, and 100/-9 for the next part. So I suggest to sell White Whip and Bloody twyre for bullets.

You can also turn your twyrine extracts into antibiotics using small device. After you made an extract you can combine it with some organ/blood. The effect depends on what you are mixing

1) Add a healthy organ/blood
You'll just waste both organ and extract, this "dead gruels" will not change infection level and do the same health damage as extract you used for mixing

2) Add an infected organ/blood
No matter which organ you used, effect will be the same: +Immunity stat will change to -Infection stat (capped at 97%, you cannot completely heal infection with it, you can only slow it down and buy yourself some time, same as using antibiotics), and it will do the same health damage as extract you used for mixing


3) Add a quest item
No matter how bad your extract was, you'll make the cure. It will destoy infection at any level without any health damage. But these quest items are very limited and you can get them only in quests (~6 in entire game).
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If you are asked to make some extracts for quests, you can make anything you want -6/-6 from one Bloody twyre or even 0/0. You are the only one who understands how it works so you can fool everyone. Poor people, you are 'helping'.