I have a theory that the Duke we see in game is actually the personification of the Megamycete itself. This came to me mostly from the fact that the Duke knows EVERYTHING. He knows more than Ethan, Mia, Chris and Miranda combined including everyones most guarded secrets. Megamycete is presented as superorganism with combined knowlege of everyone and everything that came into contact with it (mostly by perishing and getting burried) and it is also indicated that all infected by mold have some kind of psychic conection. This could mean that megamycete could have all this information.
I also considered Duke's motivation to help Ethan. The Duke claims that his motive is monetary gain but I highly doubt he has anything to gain from Ethan who is just plundering massacred village in which he came empty handed. The duke even expends more money by buying corpses of fallen enemies (I din't count this but I come from Ethen usually having lot of surplus money at the end of the game). It is true that the Duke might sell those corpses later for profit but I am not convinced. Even Ethan doesn't trust the Duke's explanation but he does not have time to solve this mystery when he has Rose to save. But claiming monetary interest is easy explanation to deflect other questions and hide Dukes't true motive. While Miranda and most of her creations are clearly mad and evil, the Megamycete is neither of those. I would argue Megamycete personality is benevolent and non agresive. When Miranda first found it, she was sick and nearly dead. She got infected by mold but she got healed and gained powers. I thing everything bad then came from Miranda and her mad quest of revivng her dead dauther not from the Megamycete. If that is true then the Megamycete would se Ethan as an opportunity to save itself from Miranda abusing it for her means and it would try to help Ethan by providing guidance, support and sanctuary from other infected as the Duke does. Collecting corpses for the Duke now makes more sence because Megamycete uses corpses of the dead to absorb them into his network.
I looked further for evidence to support or disprove this theory. There are few mentions of the Duke namely villiger's diary and guest book in the castle. From those it is almost clear that there was merchant named The Duke before main outbreak in the village, but you actually never see anyone other than Ethan to interact with him during the game. My theory is that the merchant died during the oubreak before Ethan arived and his consciousness and personality got absorbed by the Megamycete. Megamycete then chose the Duke as his avatar to communicate with Ethan.
This would also explain all of Dukes amazing feats like being able to get anywhere faster then Ethan despite being virtually immobile. Ethen is also unable to shoot the Duke just like he could not shoot at Eveline(AKA the Grandma) in RE7.
When duke helped Ethan one last time before the game final Ethan asked him who or what he really is knowing Dukes previous claimes just don't hold up. Duke replied that even him can quite answer that. In this theory that answer actualy makes sence because explaining nature, origin and motivation of a organism such as the Megamycete would be probably imposible in general.
Last thing I want to mention is fact that Megamycete got destroyed during the finale of the game. I believe that this outcome was intentional by the Megamycete. After Chris managed to defeat monster guarding the Megamycete (clearly creation of Miranda) there was no further resistence from the core iself despide it being clearly able to control the mold tentacles. Secondly the Megamycete (considering it is in fact benevolent and non-agresive) would see that his continual existence would in time led to another evil person abusing it and/or using it to hurt others. In that case would be logical to seek and welcome its own demise.
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Ufff that was longer then I intended. someone please someone point me to some clear evidence that disproof this so I can forget about all of this

Thank you
