The Case Study of Vanitas: Who is Naenia?

gamerant.com:

Warning: This contains spoilers for The Case Study of Vanitas

The corruption of true names and the ringleader of the Parade of Charlatan is not Vanitas, Vampire of the Blue Moon, like everyone believes. That honor goes to Naenia, a shadowy figure who, for reasons unknown, desires nothing more than to defile the true names of vampires. This boogeyman figure serves as the main antagonist in TheCase Study of Vanitas.

She hunts down vampires and haunt them, torturing them with visions, fears, and nightmares, until they give her their true name. Naenia takes their name and corrupts it, turning them into a curse bearer, a violent, bloodthirsty creature who will stop at nothing in order to kill everyone around them, similar to an akuma in D. Gray Man. She had followed Lord Ruthven during the war with the humans, and stalked Chloe d'Apchier after she and Jeanne parted ways. She had successfully tortured the true name out of Amelia Ruth, Louis de Sade, but Jean-Jaques gave his to her willingly in order to become stronger. Most of Naenia's victims die at the hands of a Bourreau, putting them out of their misery and keeping other safe. It is only with the appearance of a human called Vanitas that Naenia's victims have some form of hope.

Best Anime On Crunchyroll (March 2022)

Naenia's appearance as being of pure shadow with red eyes and a twisted opaque smile match her monstrosity perfectly. She appears to have the ability to appear anywhere and interact with different people at the same time. Only the golden claws and bracelet on her right hand give a clue to Naenia's true identity Queen Faustina, the first vampire of the Crimson Moon.

Not much is known about the vampire queen other than her incredible strength. Her power is so immense