We have a full clan of ten people, and have been playing Siptah since its’ release. I can assure you there is no midnight alchemist recipe on the island. You CAN get potions of Bestial Memory from certain one-skull bosses (we’ve gotten them from Hyenas, yetis, and wolves) but they are extremely rare.
Please Devs, throw us a bone. Put the midnight alchemist recipe in the map.
I’ve given up hope. I just make sure to kill the black yeti bosses (or whatever they’re called), harvest their corpses with a star metal pickaxe, and if that drops potions of bestial memory, I put them into my follower’s inventory to transfer to a fridge when I get back to my base.
I have a pretty good stash now, but I wish I didn’t have to do that. It’s yet another frustrating slot machine game mechanic and I hate it.