I mean, he doens't have any notes of Legion and the new killers, maybe he lost all hope and became one of the killers?
He is probably dead
He's probably a husk now :/
My suggestion is that he is The Observer.
he is not the alchemist?
(Hallowed blight-hallowed catalyst)
That is unlikely, considering that in the first batch of lore about the Alchemist before the tomes, the one thing that he remembered before the trials was being in opium dens, something that as far as we know, Benedict had contact, given that he disappeared while searching info about the crimes that Evan caused. That lore also shows that he is not Vigo either, as the info that he gains from the petals is from stuff that Vigo left behind:
It is impossible to describe the horrifying scenes I have witnessed... death and misery, in every shape of terror, rule this place. I can no longer recall how I have come to this place. All I remember is the opaque, milky fumes of opium in the murky den hazing a sweet, welcoming abyss. I awoke to dreadful screams in this endless night, at the feet an old tree that leaked foul-smelling fluids. I know not how to reach those poor souls, nor do I want to. Keeping a record is all I can do to make sense of it.
I personally think the alchemist is Vigo
The issue is that in the next lore(that I forgot to include), the alchemist talks about finding info from Vigo himself, so it doesn't make sense for him to be Vigo:
I discovered a hidden laboratory while running away from a monster. Its stocks are uncommonly plentiful. I observed shelves of alkaloids, crates of silver syringes, piles of protective clothes and a journal signed “Vigo”. Its pages are filled with notes on an ancient force that controls the nature of this place—that shapes it. I also noted a few drawings of the growing cankers I've seen on trees.
I should have foreseen his escape, given the potent dosage I administered him, but I needed to see results. Pustula flowers are now blooming on the path leading to the laboratory. According to Vigo's Journal, this rapid spread is a sign that the blight is at its peak. Soon, there will be no more putrid nectar to extract.
Based on Vigo's calculations, tonight is my last chance. I filled a syringe with the last drops of serum and injected it into my arm.
I looked for Vigo. I shouted his name with no concern for the monsters lurking about. I need to find him… I picture the scene, etching a canvas of wild lines in my mind, focusing on the moon and I know—something is off. I fed the dead rodent under my pillow.
Besides, I seem to remember devs talking about Vigo being the one responsible for the creation of the hatch, the gens and other stuff, which the Entity took inspiration to use in the trails.
Who is Benedict Baker and Vigo?
Mathieu - "These would actually fill a few books."
Dave - "These characters have been there for a long time. Vigo has been, and Benedict is, a Survivor. It's established that Benedict is still in the realm of The Entity, still surviving. He's someone who, in the real world, was looking into finding The Entity's realm. We know [Vigo] is a researcher, inventor. Out of the quotes in the game, we know he invented some of the contraptions. He also researched the biological aspect of The Entity."
The hallowed blight lore makes refrence to the fact that the Entity took him from the trials... to where, or why, we really have no clue.
Oh I didn't see that
That was resolved in the next blight event, where it was shown that he was thrown into the Void, spent some time there and eventually made a deal with the Entity to get out, implying that he was going to become a Killer. My theory is that the Alchemist will be sent against the Observer and will probably not be a playable killer for some times, perhaps building him up as some super Killer of some kind.