Klaus looks like a Bavarian young man who has slept in too many borrowed rooms: wiry, restless, and perpetually dusted with the Lodge's pale lint. In his fae mien, long rabbit ears replace his human ears, and branching antlers rise above his brow. His ears swivel before his head turns. His clothes are practical but ill-fitting, repeatedly darned at the elbows and hem; one green wool scarf is brushed clean and carefully folded even when everything else is rumpled. He smells of damp hay and clove soap, a fact he denies noticing. His movements are quick starts and abrupt stops, as if every doorway might be a bolt-hole. The antlers make him look more imposing than his habit of sleeping under tables would suggest.

Klaus is wary of hospitality but quick to defend anyone who has offered it. He can be nimble and joking while scouting, yet becomes stubbornly solemn when someone is in danger. He dislikes being managed, though he quietly follows Johanna's instructions when her employment is at stake. He wants to be dependable and fears that his escape-first instincts will prove stronger than his promises.

Klaus grew up in Bavaria, where his first name was Klaus and his family expected him to take steady work and stop vanishing whenever a room grew crowded. His fae nature surfaced in adolescence, along with the rabbit's ears and the habit of seeing the Dreaming's seams at the edge of familiar places. A bad winter changed his course: he followed a half-seen path into a dangerous dream-realm and left a frightened companion behind while he escaped. He has never excused himself for it. Since then, he has tried to be the one who stays behind to hold a route open. He reached the Lodge with Marine, Adriene, and Johanna, all regarded by its residents as invaders. Johanna works at the Lodge and often conceals the Wolpertingers from its other inhabitants. Klaus spends much of his time hidden in the Lodge's Dreaming reflection, mapping doors, service passages, and places where the two worlds nearly touch. He is a freeloader by reputation and often by fact, but he repays shelter with watch duty and warnings. His present problem is that a route he once used has begun leading somewhere unfamiliar, and he suspects his old failure has followed him there.