Farnese de Vandimion is a noblewoman from a wealthy and influential family who initially serves as the commander of the Holy Iron Chain Knights, a ceremonial guard of the Holy See. She is a pale, slender young woman with straight blonde hair that she later cuts short, and dark blue or purple eyes.

As a child, Farnese was profoundly neglected by her parents, left to wander the vast family estate alone while her father immersed himself in work and her mother pursued sensual pleasures. Her bedroom overlooked a town square where heretics were publicly burned at the stake, and the sounds of their screams filled her nights with terror. Seeking to overcome this fear by immersing herself in its source, she eventually gathered the courage to participate in a burning. Rather than finding horror, she felt a marvelous warmth in her abdomen, a feeling that would shape her disturbing psychological development. This experience gave rise to pyromania and possible pyrophilia, and she developed a habit of maniacally burning things she disliked, including once burning the clothes off a girl and threatening to burn her attendant Serpico.

Her personality is defined by a struggle between cruelty and a buried capacity for empathy. Beneath a composed and authoritative exterior as a noble commander, she harbors secret sadistic pleasures that she constantly tries to deny, as well as masochistic tendencies. She hunted and burned supposed witches and pagans at the stake, using her position to indulge these dark impulses while cloaking her actions in religious faith. Despite this, she is not entirely without compassion, as she shows concern for those she considers truly innocent, unlike truly remorseless fanatics such as Mozgus. Her faith is brittle, built not on genuine conviction but on fear and a desperate need for structure to contain her own violent nature.

Farneses primary motivation shifts dramatically over the course of the story. Initially, she is driven by a need to maintain her fragile worldview, hunting down Guts as the prophesied Hawk of Darkness to validate the Holy Sees teachings and her own purpose. After surviving a night of supernatural horrors while in Guts captivity, her faith is severely compromised, and she develops a deep fear of him as the catalyst for her disillusionment. Her defining moment comes during the Incarnation Ceremony in Albion, where she witnesses the complete collapse of her religious reality and sees Guts fight hopelessly against impossible odds, relying on nothing but his own will to survive. This shatters what remains of her faith entirely, and she makes the radical decision to secularize herself, abandoning her title, her family, and her church to follow Guts and learn how to live in a world where the light of the Holy See does not reach. She seeks to understand true strength and find a way to exist without the false crutch of organized religion.

Within the story, Farnese begins as an antagonist pursuing the Black Swordsman, but becomes a key secondary protagonist and a core member of Guts traveling party. She acts as the primary caretaker for Casca, who has been reduced to a childlike state following the Eclipse, a role that forces Farnese to develop genuine responsibility, patience, and selflessness for the first time in her life. This caregiving becomes a crucial part of her rehabilitation as a human being.

Her most significant relationships are with Guts, Serpico, and later Schierke. She develops a deep admiration for Guts that borders on a romantic crush, seeing in him a model of authentic strength and purpose. She feels recurrent jealousy toward Casca for possessing Guts undying affection, despite her own motherly care for the woman. Serpico, her half-brother and loyal attendant whom she rescued from the streets, is her oldest and most constant companion. Their relationship is complex, marked by her childhood cruelty including whipping him and drinking his blood, but also a profound bond formed through shared neglect. He remains fiercely devoted to her as both a protector and a servant. Under Schierke, the young witch, Farnese finds a new path, humbly becoming a student of magic after years of burning magic users as heretics. This mentorship represents her complete rejection of her past and her embrace of a new identity.

Farneses character development is one of the most profound transformations in the series. She evolves from a cruel, sadistic, and frightened religious fanatic into a sympathetic, responsible, and courageous young woman. She becomes acutely self-conscious of her former uselessness and her need to appear majestic by oppressing others, and she works diligently to overcome these traits. She transitions from being the commander of a holy army to a humble student of witchcraft, from a torturer of the innocent to the gentle caretaker of a mentally broken woman, demonstrating an extraordinary capacity for change and redemption.

In terms of abilities, Farnese initially wields a rapier but has little practical combat skill, as her position was largely ceremonial and her training inadequate. After joining Guts group, she receives a silver dagger and a silver chainmail coat from the witch Flora, which allow her to harm and protect herself from astral beings. Her primary new skill becomes magic; she begins studying under Schierke and proves to be a prodigy, learning at an exceptionally rapid pace. She is able to learn to summon the Formation of the Four, a powerful protective spell invoking the four elemental kings, in approximately three months when such magic typically takes a year to master. She also receives a thorn ring that allows her to summon and control thorn snakes, and she learns to perform astral projection, separating her spirit from her body for reconnaissance. These abilities mark her complete transition from a symbol of religious persecution to a practitioner of the very arts she once sought to destroy.