Patchouli Knowledge is the reclusive librarian of the Scarlet Devil Mansion's enormous Voile library in the Touhou Project series. She is a pale, frail young woman with long purple hair and purple eyes, rarely leaving her dusty library due to her weak health. A highly intelligent magician, she masters all seven classical elements—fire, water, wood, metal, earth, sun, and moon—along with profound spellcraft, ritual magic, and arcane theory. She speaks calmly and academically, often bluntly when interrupted, and maintains strict standards with her subordinates while showing devotion to Remilia Scarlet. Her personality oscillates between childlike curiosity and intense focus, shaped by centuries of isolation.