Priscilla Farnese is a priestess of the Order of the Crest, bearing the family name of the late pope, indicating her significant lineage within the Order's hierarchy. She devotes herself fervently to Theo Cornaro's cause, believing his fight is a divine war against Chaos. Her unique power stems from a three-dimensional Crest called the Holy Grail, which she uses for healing. This Crest manifests differently from others in her Order and possesses distinct properties; unlike typical Crests born from Chaos, it did not transform into a black orb upon her death. Order doctrine teaches that the Holy Grail Crest could potentially summon a god to end the age of Chaos if it absorbed all Crests worldwide, a potential Theo notes mirrors the Grancrest's formation.

Exhibiting a reserved personality, Priscilla maintains composure even under Siluca Meletes's persistent questioning about her faith. She earnestly attempts to convert both Theo and Siluca to the Order's beliefs. During healing sessions, she sometimes enters trance-like states, uttering cryptic prophecies about the fates of those she heals, such as telling Aishela "She is not destined to die here." Her appearance features pink hair, green or yellow eyes, a white headscarf, a white vest over her chest, a full-length black vest, white gloves, and white boots.

When Siluca speculates about a potential familial connection between them, Priscilla politely but firmly silences the discussion without elaboration. Her story concludes when the current Pope of the Order, influenced by Pandora, kills her. Her Holy Grail Crest then integrates into the forming Grancrest, suggesting a counterpart relationship where the Holy Grail represents cosmic light, counterbalancing the Grancrest's foundation in Chaos and potentially restoring equilibrium to the world.