|“||Wormwood… the bright star shall fall from the sky… and many will die from its bitterness.||„|
|~ Yerzinia's prophecy.|
Before the book
She was said by her brother Abram to have been the cause of the Jewish genocide in Prague in 1621 and she was the creator of the Golem that stalked the streets. Back then, she called herself Baroness Manrique de Moya. She was always an incredibly beautiful lady, being vain, seductive and persuasive, and it is suggested she set the Great Fire of London deliberately in 1666.
During the book
Like her brother, she is completely irredeemable, and has caused countless disasters throughout human history. Also unlike Pyratheon she does not openly announce herself because, unlike him, she values caution. She is always noticeably driving majestically round London in her dark funereal carriage, pulled by majestic black horses.
She kidnaps and summons Agetta Lamian, the protagonist and a servant girl, into her coach where she threatens Agetta with her dog's murder if she doesn't comply to her desire. Agetta is told to seek out Thaddeus, a bookkeeper, because he most likely holds The Nemorensis, a magical grimoire which holds the secrets of the Universe. Agetta finds that Thaddeus long ago lost the book, and remembers her master, Sabian Blake, also one of the main protagonists in the novel, has the book.
So Agetta steals the Book and also makes off with Tegatus, a fallen angel who was being tortured alive in her family attic. Agetta makes her way through London.
In the meantime, however, Blake is being wined and dined by Lady Hezrin Flamberg, who is not so subtly revealed to be Yerzinia in disguise, because she acted exactly as Yerzinia does, and, like Yerzinia, Lady Flamberg is very beautful, seductive and bold for a woman of her era. She says she started the Great Fire and it is her desire to wipe out the scum of London and begin a new order. Blake is disturbed by this revelation, and he yells for the public to listen, but no one does.
Yerzinia, as Flamberg, leads Blake into another world behind her ancestral mirror, and next thing he knows, he awakens in a grave, about to be buried alive. Yet Abram saves Blake, and proves he is an angel by resurrecting a murdered nobleman, yet Blake still refuses to believe Abram's divinity.
Yerzinia hastens all her allies to hunt down Agetta and make way for the recovery of The Nemorensis and hasten the Apocalypse....
Thaddeus betrays Tegatus, Agetta and Blake to the demons and Tegatus renders the bookseller unconscious. However Yerzinia summons Thaddeus and presumably learns of the events of the past week from him, including Tegatus' location.
As the stars fall from the sky and the dead begin to rise, Abram rallies Blake and Agetta to return Tegatus to the armies of Heaven and fight the gargoyle demons which have come to life. A battle begins on the roof of Thaddeus' bookshop. Isaac Bonham, Blake's former friend, is revealed to be Yerzinia's treacherous lover. He apparently shoots Blake dead when Blake attempts to stop a demon named Morbus from sacrificing Agetta. It is Yerzinia's plan to possess Agetta's body so she can remain young and beautiful and sacrifice her ultimate fate of being turned into a Diakka (a demonic rank).
Yerzinia announces how the Apocalypse is on humanity and she prepares to sacrifice Agetta. Opening her mouth wide, she rips off her mask and asks Agetta if she is ready to repay her debt. The Nemorensis grows to the height of a tower, and Agetta is so deeply brainwashed she admits her lifetime servitude to Yerzinia. Abram yells that Agetta doesn't know what she is saying but Yerzinia confirms she does, and Yerzinia's angel essence escapes her mouth to seek Agetta out to posses her. But Yerzinia's essence is still tethered to her mortal body. She needs to possess a new body to regenerate every thousand years, yet her chance to possess Agetta is destroyed at the moment of her triumph when Tegatus, wounded to death by an exploding Abaris crystal, rushes into the battle and rips the silk crimson cord off The Nemorensis, causing it to return to its standard book form. Diminishing in power, Yerzinia is dragged from the rooftop by the fallen angel, as Tegatus wraps the cord round Yerzinia and drags her into the whirlpool on the banks of Fleet Street. She screams in anguish as Tegatus' affliction infects her and she rapidly ages to a grisly old hag. But as she screams that not even death will stop her, her last efforts are all in vain, because Yerzinia is rapidly consumed by the swirling whirlpool and destroyed, along with Tegatus.
Abram awakens Blake and summons him to protect Agetta, saying that the war is not yet over and Bonham will try again to kill them both. Urging caution, Abram departs.
Yerzinia was a very vain, selfish and egotistical character. Unlike her brother, she valued caution and was not a lady of action, only interfering when all seemed well and playing as she had planned, yet she could still be prone to her brother's mistakes of overconfidence and lust for dominion. Not content with wanting to rule Earth, she desired to rule Heaven too. And turn Earth into Hell, like as not.
Formerly one of the most beautiful angels in existence, Yerzinia used to be the scribe of Heaven before she was banished for plotting universal conquest. She wrote her bitterness and envy of humanity in The Nemorensis, which she had originally wrote as a family history of God and his angels. However, she was stripped of her angelic grace by the time she fell.
Her true character is revealed in the last pages of the novel, where she is transformed from the beautiful young lady she is into a wicked old witch.
Yerzinia was very lustful, desiring both men and power, and she may have been bisexual, because there is somewhat of a sexual way she speaks to Agetta, and desiring Agetta's body may indicate Yerzinia was slightly lusting for her, both spiritually and sexually. She discarded men after they were done, having proved their usefulness and then thrown into the trash of humanity. Such was the workings of a fallen angel.