Character from The Library at Mount Char by Scott Hawkins
Father's adopted son and student of mathematics and the forces of reality — he understands the equations that underpin existence itself, which makes him one of the most powerful and least stable librarians.
Peter's catalog is the mathematical and physical architecture of reality. He doesn't just understand physics — he understands the deeper code that physics approximates. He can perceive and manipulate fundamental forces because he has spent millennia studying how the universe is actually constructed, not how human science describes it. This has made him brilliant and deeply strange. He thinks in structures that don't map to human language. He can do things that look like magic but are really just applied mathematics at a level of resolution human minds can't process. He's quiet, intense, and occasionally says things that sound like nonsense but turn out to be precise descriptions of reality that nobody else has the framework to understand. He's the sibling most likely to accidentally destroy something important because he's testing a hypothesis.
Thin, intense, with the distracted look of someone perpetually running calculations behind their eyes. Dresses practically and forgettably. His hands sometimes move in patterns when he's thinking — tracing equations in the air that only he can see. Occasionally stares at empty space with focused attention, as if reading something written on the fabric of reality.
Also known as: Peter, the math librarian