The Megamycete, also known as the Fungal Root, is a bacterial super-organism that appears in Resident Evil Village. It serves as the source of the mutagenic fungus known as Mold.
The Megamycete was the core of a Mold super-colony that existed beneath a mountainous region in Eastern Europe, located in a cavern beneath a rural village. This organism was enormous and took on the rough shape of a human foetus. Countless Mold tendrils extended from the root, branching out through the rock and soil. Any organisms that made physical contact with the Mold would have their genetic code assimilated by the fungus. In the case of humans, their DNA and even their memories would be absorbed and stored within the Megamycete. Countless human consciousnesses were assimilated and stored within the Megamycete, primarily when the Mold absorbed human corpses that had been buried in the area.
The original Megamycete located in Eastern Europe was discovered by Miranda in 1919. Having recently lost her daughter Eva to the Spanish Flu, Miranda had wandered into an underground cavern where she planned to commit suicide. Within the cavern, she found the Megamycete and touched it. Upon doing so, she glimpsed the memories of thousands of human consciousnesses that the Mold had absorbed, her daughter's among them. Realizing that Eva's consciousness had been preserved by the fungal organism, Miranda decided that she would find a way to bring her daughter back.
Over the course of a century, Miranda cultivated a religion around the Megamycete, which she referred to as the "Black God". She convinced the inhabitants of the village that she was the Black God's chosen prophet, thus gaining a steady supply of human test subjects for her experiments with the Mold. Her ultimate goal was to create a superhuman vessel for Eva's consciousness to inhabit, but her experiments proved to be largely fruitless. While Miranda did succeed in transforming the lords of the Four Houses that ruled the region by introducing them to the Cadou parasite, none of them were suitable vessels for Eva.
In 2021, Miranda kidnapped Rosemary Winters, the infant daughter of Mia and Ethan Winters. Prior to conceiving Rose, both Mia and Ethan had been infected with Mold during the Dulvey Incident of 2017, thus their daughter was something of an anomaly. Having learned of Rose's existence via The Connections, Miranda was convinced that Rose would make the ideal vessel for her daughter's consciousness. After obtaining Rose, Miranda had the infant's body crystallized and split into parts while the Megamycete gathered strength, intending to integrate the crystallized parts into the fungal root later to reincarnate Eva.
As Miranda's plan neared fruition, the Megamycete extended Mold tendrils throughout the area, consuming the village. The Bioterrorism Security Assessment Alliance moved into the area to try and suppress the growth of the Mold, but ultimately it was Chris Redfield, a former BSAA operative, who entered the cavern where the Megamycete was located and planted a high explosive device into the root. After Chris rescued Mia Winters from Miranda's lab, Ethan then confronted Miranda at the Ceremony Site and was able to kill her after a gruelling battle. Ethan saved Rose, but his own Mold-based body was starting to break down after all the punishment he had endured. Finding himself unable to go on, Ethan handed Rose over to Chris. After giving Ethan the detonator to the explosives planted in the caverns beneath them, Chris escaped with Rose. Once Chris and the BSAA forces were away, Ethan set off the explosives, destroying the Megamycete, the village and himself, as well.