Mutations are central to the story of Resident Evil Village, just as much as the parasitic origins of mutations have been central to every Resident Evil game that came before it. However, things are a bit different in Village, because there are some very different mutations this time around. No longer are the walking dead the key enemies in the story. Neither is the kind of living zombies that were the Bakers in Resident Evil 7. This time around, several of the monsters that popped up in Village were more closely tied to older monster lore, though they had their own Resident Evil twist.
There are actually three different kinds of "mutating" compounds that play a part in Resident Evil Village. Megamycete, Mold, and the Cadou Parasite all contribute to the chaos that takes place in the game in very different ways. The Megamycete appears to be a kind of "hive-mind" organism that can take over, or at least partially control, its host. The Mold appears to be part of the Megamycete so it's not entirely separate. Some characters in Village talk about it as though it's the fungus that allows the Megamycete to infect a host. Finally, the Cadou parasite is another offshoot of the Megamycete, but more central to Village.
Mother Knows Parasites
As Mother Miranda is responsible for most of the chaos of Resident Evil Village, it should come as no surprise that she is also responsible for the Cadou parasite. It seems as though she first discovered the Megamycete when she was wandering around in grief over the loss of her daughter. She came about a cave that served as a home for the organism and became infected. Miranda then decided to start experimenting with mold samples so she could better infect others. The other end goal for those experiments was to find a way to resurrect her daughter.
During her experimentations with the mold, Miranda discovered it would be easier to make the mold take on the form of the Cadou parasite — meaning "present" or "gift" in Romanian. While many of the people infected with Cadou became Lycans or other monstrosities, the four Lords of Resident Evil Village had very different reactions to it. It's not entirely clear why those reactions were so different among those four, but it's clear it's one of the reasons they remained near the top of the "food chain" in Village.
Miranda's Lords
Of the four lords of Resident Evil Village, it appears that the Cadou parasite allowed Dimitrescu to keep more of "herself" than even Moreau, Beneviento, and Heisenberg. This might be why she seemed especially close to Mother Miranda. Her transformation also shows how the Cadou parasite adapts and changes people quite differently. In Lady Dimitrescu's case, it accelerated and changed a blood disease she already had. That's both why she takes on the appearance of a vampire and the real reason she has to drink human blood.
As the game shows, each of Mother Miranda's lords does find a way to control the Cadou parasite, even as they are all changed differently. The one big question left unanswered about the Cadou parasite is: Why do s ome seem completely under the influence of the parasite, while others seem to bond with it? As Dimitrescu, Moreau, Beneviento and Heisenberg are able to do.
Resident Evil Village is available now on PC, PS4, PS5, Stadia, Xbox One, and Xbox Series X/S.