The aspect of decay would be the only similarities. There is no otherworldly influence or affliction upon the characters beyond what's purposely caused by the ritual.

Visual images of both Koth and the Mysterious Acolyte are provided in their respective Event posts, so you can decide how you want your character to interpret their appearances based on those images, and whether they would believe that the two share a relation. The Mysterious Acolyte's hands, which are the only visible parts of her body from beneath the robes, would appear mostly humanoid aside from growths across her skin like the ones on her facial features.