Nightingale is the first witch from the Witch Cooperation Association to come into contact with Roland. She is a former assassin that currently serves as Roland's personal bodyguard as well as the head of Graycastle's Security Bureau. Nightingale's real name is Veronica Gilen, which she chooses to rarely use as a rejection of her past life.
Nightingale is a slender young woman with mature, charming features. Her blond hair cascades down like a waterfall. At her first meeting with Roland, she wore dark clothes with a hood, hiding her face. After joining the Witch Union, Roland gave her a set of clothing based on the white hooded cloak worn by protagonists from the Assassin's Creed game series; a private joke of his in reference to her identity as an assassin.
For sleepwear, Nightingale initially wore a nightgown in the early days of the Witch Union. She later switch to simply wearing a camisole.
Nightingale is a woman who follows her own personal view of right and wrong. After her grueling experience under her uncle, she decided to never cry or be afraid of what comes her way, making her a courageous and strong-willed woman.
She also has a mischievous side, pinching Roland whenever he does something she finds annoying or stealing his food without his knowledge or consent.
She is very overprotective of Roland, and her loyalty to him is unwavering. She would gladly lay down her life to protect him. Nightingale spends most of her time eating dried fish near him and will try to always be invisible by his side whenever he is meeting with someone else. She also put a god's stone of retaliation below Roland's pillows for his safety. Roland's safety is her upmost priority, and she is prone to place blame upon herself when she fails to protect him from harm.
She is jealous of Anna's close relationship with Roland and frequently wishes that she had met Roland first.
She has very little tolerance for anyone who insults, verbally abuse, or threatens Roland. While she normally keeps her emotions in check in order to perform her duties, she is prone to the occasional outburst and will sometimes take matters into her own hands without Roland's consent.
In the winter when she turned 14, both her parents disappeared mysteriously while on their way to deliver food to the hungry people in Silver City. A few days after their disappearance, Veronica and her little brother Hyde were sent to the home of their uncle, Mr. Gilen.
After living with her uncle for a few days, Veronica awakened her invisibility powers and became a Witch. Eventually, the apathetic Mr. Gilen discovered Veronica's powers and her identity as a witch. Thinking that Veronica could be useful to him, Mr. Gilen started using Hyde's life as a hostage and sent her to the thieves’ guild and made her undergo assassin training for a few years so that he could use her as a tool to eliminate his political rivals and obtain more power within Silver City.
Mr. Gilen's attitude towards Veronica was gradually turning worse as time flowed. He started to physically abuse her and shut her inside a dungeon-like room with no connection to the outside. Veronica bore the abuse and her terrible deeds as a Shadow Killer, as it was the only way to safeguard her dear little brother's life, even so her mental state was continuously deteriorating more and more as days passed.
After persistent requests of asking her uncle to let her meet with her little brother, Mr. Gilen finally did, but when she saw Hyde, he was changed, and he told her that they were siblings no more and that he never wanted to see her again because she had become a demonic witch. After this event, Mr. Gilen grimly warned her that Hyde would now inherit their father’s title as Viscount of Silver City, but if she didn't obey his orders, he still could take her brother's life. Veronica's world collapsed, broken, she fell into sorrow and became an almost mindless puppet manipulated by the Gilen family.
Some time later, just the day before her coming of age, on her way back to the Gilen mansion after completing another task for the family she met a mysterious lady called Wendy, who told Veronica everything about the Witch Cooperation Association and that if she wanted she could live safely as a witch with them, this sparked hope again to Veronica’s poor life.
One week after this, Veronica had managed to survive and overcome the torture and pain of the changes in her magic power, with her new abilities she discovered that she could now access a new world where everything was made of fog, after grasping how this new power worked she managed to get out of her prison and immediately after stepping into Mr. Gilen’s bedroom took her assassins gear and slit his throat, putting an end to all her years of pains and saving the life of her brother for a last time.
- While a part of the Witch Cooperation Association, she was also known as the Shadow Assassin.
- Her weight was suggested in chapter 292, in which Roland's thoughts mentioned that a 250-kilogram bomb was about 5 times Nightingale's weight, meaning that Nightingale weighed about 50 kilograms, or about 110 pounds.
- Nightingale has difficulty understanding the lessons given to the witches, which leads her to oftentimes be jealous whenever Roland and Anna are having an in-depth discussion about science.
- Among the witches from the Witch Union, she's always the last to wake up. Granted she doesn't go to bed until Roland does; she watches him like a hawk for his safety.
- Nightingale's preferred weapon of choice are her two custom-made, silver revolvers, as they were handcrafted and gifted to her by Roland. Each revolver were decoratively carved "To Veronica" on their barrels.
- Nightingale is also an expert in knives, a skill she relied heavily on, prior to receiving small firearms training.
- She has a habit of picking up snacks at night from the kitchen, to the point that the chef would grill any remaining fish for her.
- During peaceful days, it was implied that she used her ability to steal dried fish from Roland's drawer all day long.
- According to Honey's messenger Owl, Nightingale is always seen sitting in Roland's office when nobody is around and constantly leans in with her arms on his desk, close to him.
- During exams, it's shown that Nightingale does worse each time, despite starting along everyone else,
- Nightingale, Maggie, and Andrea are considered the worst students when it comes to learning. Granted any "free space" in her brain was taken up by assassination skills at a young age; she does, however, still manage to be polite and give off the air of a noble.
- As an assassin trained by her uncle in the past, Nightingale is considered one of the strongest and fastest witches in the series. This is proven by the fact that Leaf considered her to be one of the strongest witches in the Witch Cooperation Association, meaning she is as strong as Cara, or that she might even have a chance at defeating her.
- Chapter 63 (novel)
- Here and below: Chapter 63
- Chapter 575 (novel)
- Novel Chapter 96