Patchouli Knowledge is a magician who resides in the Scarlet Devil Mansion. She's good friends with the mansion's mistress, Remilia Scarlet, and spends most of her time in the mansion library. Well-versed in spirit magic and its five Phases, she's also adept at performing intricate tasks. Patchouli frequently asks the mansion's head maid, Sakuya Izayoi, to investigate things for her, and it's thought that she summoned Koakuma to be her familiar.

The Scarlet Devil Mansions stands on the shores of the Misty Lake and is home to vampires. It's also where Patchouli resides. The fact it's far bigger on the inside than it appears from the outside is supposedly the maid's doing. The mansion has few windows, but it seems the library, which is filled with books that would rather not be exposed to sunlight, has barely any at all.

The term "magician" can be used to refer to a member of the magic-using species or someone who uses magic in their profession. The magician species includes both those who were born magicians and those who became magicians later in life. Since the definition of magic is broad, there are many humans and youkai who could conceivably be called magicians. In more specific terms, Western-style magical techniques and techniques that clearly deviate from the Buddhist Middle Path are referred to as magic, and it's common to call users of such techniques magicians.

Defining magic is tricky, and you wouldn't necessarily be wrong to refer to all special abilities as magic. Although, perhaps you could refer to any technique that hasn't already been fully explained by science or some other illuminating tool of human civilization as magic.

"...That's the end of my report." "That can't be." "Um, rude." "I didn't mean it like that, Marisa. I was talking about the situation you described. It's very confusing." "You don't have to tell me that. I'm seeing it right now, and I still don't understand it. So, what are we gonna do?" "Hmm..." "..." "First, let's talk about that other phenomenon that recently ceased. What could it have been...?" "That ended ages ago!"