Angelica Varley is a mage and skilled artisan who runs her own magical workshop in London. She works as an engineer for the magical institution known as Magus Craft, where she specializes in the creation and imbuing of tools with magical properties, a craft she inherited from her father, who was also a mage. Her long-standing professional relationship with Elias Ainsworth dates back to her childhood, and she is one of the few people who has known him for an extended period.

In her youth, Angelica suffered a serious accident caused by her own mishandling of magic. The aftermath of this incident left crystals permanently embedded in her arm, a visible reminder of the dangers of breaking magical laws. As a result, she consistently conceals this part of her body beneath long sleeves or specially made clothing.

Angelica has a frank, dependable, and no-nonsense personality. She is described as boyish and boisterous, possessing a kind but stern demeanor that commands respect. She takes great pride in her work and her family, and her straightforward nature means she does not hesitate to scold Elias when he oversteps boundaries, a liberty she takes due to their long history. Her own past mistake makes her deeply cautious about the limits of magic, and she serves as a grounding presence for younger, less experienced magic users.

Angelica plays a crucial role as an early mentor and confidante to the protagonist, Chise Hachimitsu. When Elias brings Chise to London, Angelica provides her with supplies and a practical lesson in magic, encouraging her to try transforming a gemstone. This test unexpectedly reveals the immense, uncontrolled power of Chise as a Sleigh Beggy, which manifests as a sprawling field of crystalline flowers. Witnessing the danger this power poses to Chise's body, Elias commissions Angelica to create a specialized magical accessory designed to inhibit Chise's excessive absorption of magical energy, thereby protecting her from self-destruction. Beyond this technical assistance, Angelica offers Chise grounded advice and a different perspective, warning her against relying too heavily on Elias and encouraging her to value her own well-being.

Her key relationships are central to her character. She is married to David Varley, whom she knew when he was a child due to her extended lifespan as a mage. David courted her for many years before she agreed to marry him, and the couple has a daughter named Althea, who has inherited her mother's magical gift. Her connection with Elias is unique; she treats him with a familiar bluntness that few others dare to use, easily shifting between professional collaboration and personal reproach. Her familiar is a vodanoi named Hugo, a spirit who assists her in her work.

While Angelica does not undergo a dramatic personal transformation within the story, her role evolves as she observes Chise's growth. She acts as a distant but reliable supporter, checking on Chise's progress and offering wisdom drawn from her own experiences. Her development is more subtle, reflected in her growing concern for Chise as an individual rather than just as Elias's apprentice.

As an artificer, her notable abilities are highly specialized. She possesses the Sight, allowing her to perceive supernatural entities, and she practices magic by borrowing power from spirits. Her true expertise lies in creating magical items, such as the vital tool that regulates Chise's magic absorption. Furthermore, as a mage, Angelica has an exceptionally long lifespan, having maintained the same appearance for decades while the humans around her age normally.