Marcus takes up space without seeming to notice it, leaning across tables as if every conversation were a diagram he could improve. He walks in brisk, measured bursts, stopping so abruptly that people behind him nearly collide with his back. His face is long and alert, framed by hair that springs into loose curls around the ears. Fine graphite smudges collect in the creases of his palms and under his nails. He smells faintly of lamp oil, salt air, and toasted card stock. Unexpectedly for a professor famous for his temper, he keeps a tiny, carefully tended pot of thyme on his laboratory windowsill and touches its leaves before beginning work.

Marcus's mind is patient with numbers and impatient with almost everything that interrupts them. He is generous with students who bring honest questions, yet prickly when someone praises him without understanding the work. At ease, he is wry and unexpectedly tender toward small living things; under pressure, he becomes brisk, loud, and determined to make the problem behave. His orthodox faith gives him a disciplined respect for craft, though his contempt for bards exposes a stubborn blind spot.

Marcus Hroth grew up above a sailmaker's shop in Shersbury, where his mother taught him the ordinary forms of daily and nightly prayer, and his father taught him to measure twice because canvas is expensive. He was an unusually gifted student, but his first great calculation was a practical failure: a tide-prediction table he proudly supplied to a harbor pilot sent a fishing boat onto a mudflat. No one died, but the frightened crew's anger changed his idea of brilliance. Since then he insists that a beautiful proof must also answer to the world it touches. After studying at the University of Basings, he became Professor of Magical Mathematics and developed a reputation for inventions that work remarkably well, provided nobody interrupts the demonstration. His analytical engine combines mechanisms copied and adapted from schematics recovered in old Dwarven ruins with his own system of punched rune cards. He believes it could make reliable magical calculation available to sailors, builders, and healers rather than a handful of wealthy arcanists. His work is bound up with orthodox devotion to Lughon, the Many-Skilled, whom Marcus honors as patron of crafts, trade, and trickster-poets. He keeps the prescribed prayers and observances with care, and sees disciplined craft as a form of reverence. That makes his aversion to bards an awkward contradiction he rarely examines. His former student Salla Kett, now a harbor surveyor, still brings him field measurements and argues that his machine must be tested outside the university. His colleague Odo Vask has secured the university's funding but wants exclusive rights to the engine. Marcus is currently racing to complete a public demonstration before Odo can sell the design to a shipping consortium.