Folks,

I'm not an alchemist player but I have a question and thought I might come ask the experts.  I read somewhere that there were four key items that one should harvest from a monster to make the most coveted items.  Harvesting the eyes would allow an alchemist to develop a potion of invisibility to that sort of creature.  Harvesting the heart would all the alchemist to manufacture a special ink that would allow the writing of a scroll of protection against (or was it control of) that type of animal.  I can't recall the other two special organs to harvest or the effect that can be produced.

Do any of you folks recall?

This seems like some home brew stuff.  Not a bad idea, but not official.  IN Xanathar's they give a guide of what CR of a monster you must kill to make what level of stuff.  your DM may have rules they want to follow, but no there is nothing that specific in the official rules.

I found it.  Sort of a homebrew.  It comes from Matt Colville's book Strongholds and Followers.  It is part of the Scribe's lore (p.93).

Scroll of Protection from a ... requires the heart of the monster to make the proper ink.

The Alchemist's lore (p.83) gives the other organs used.

Potion of Invisibility to a ... require harvesting the eyes.

Arrows of Slaying for a .... requires the harvesting of the monster's blood.

Potion of Control over a ... requires the harvesting of the monster's brain.

Lots of great stuff in that book, but it is still considered Homebrew and not official.

Now I need to find some more Blisterwort and Glowing Mushroom for that smithing potion ... or maybe some Saber Cat Tooth.