Halri Vorzak is a young girl and a rogue master participating in the False Holy Grail War, serving as the true master of the Berserker-class servant Huwawa. She is a blond-haired girl, under fifteen years of age, who comes from the Borzak family of mages. Her grandfather was Odd Borzak, a mage known as the Bee User whose destructive research into creating a ghoul army led to his death. His actions ultimately brought ruin to his family, leaving Halri as the sole survivor.

Driven by the tragic fate of her family, Halri harbors a deep and powerful hatred for the world of magecraft itself. Her parents were killed by mages from the Clock Tower, the central organization of the Mages Association, who sought to steal her grandfather's research. This event shaped her entire motivation. Rather than seeking revenge against specific individuals, her goal is far more ambitious and destructive: she wishes to use the Holy Grail to dismantle the very foundations of mage society. Her plan is to render all methods of concealment used by mages ineffective, thereby exposing the existence of the magical world to the general public and collapsing the secretive system that she holds responsible for her loss.

Despite her burning desire for revenge, Halri is described as having a contradictory personality. While she despises the institution of magecraft, she is a capable mage herself, practicing a form of Witchcraft. She is notably reluctant to cause direct harm to others. In battle, she hesitates to use lethal force, and in her magical practices, she refuses to sacrifice animals, instead offering only her own flesh and blood as a tribute. Her primary skill in Witchcraft lies not in casting curses but in deflecting them. She also possesses some ability to heal herself and her magic circuits. For combat, she utilizes bees hidden in her clothing as familiars, which can be used to form a defensive barrier or to incapacitate humans by making them lose consciousness. Her capacity for direct combat is low, and she relies on her familiars for personal defense.

Halri is recruited into the Holy Grail War by Francesca Prelati, who discovers her and offers her a chance to achieve her goal. On the first day of the war, she attempts to summon her servant, True Berserker, in a thermal power station. However, the servant is uncontrollable and goes on a rampage, attacking her and tearing through her abdomen with its claws. As she lies dying, she is saved by a homunculus named Fillia. Fillia intervenes, heals her wounds, and manages to force the rampaging Berserker into a contract with Halri. From this point, despite being the rightful master, Halri chooses to follow Fillia's lead out of gratitude for saving her life. Together, they form a team and launch an attack on the workshop of Bazdilot Cordelion, the master of True Archer. During the attack, she orders Berserker to destroy the workshop and the surrounding area. The situation is eventually brought to a temporary halt by the intervention of True Caster. Her role in the story is therefore that of a vengeful outsider whose personal mission against the mage world drives her actions, forming a unique partnership with the mysterious Fillia.