Jessa stands with the balanced stillness of someone accustomed to a floor that lurches beneath them. Their warm umber skin is finely stippled with soot that never quite washes from the creases around their knuckles, and their blunt, strong jaw shifts slightly when they listen, as if measuring a mechanism by its vibration. Their teeth are unusually even and pale; when they laugh, they show them all at once, a startlingly open expression from someone so exacting. Two ridged horns sweep back from their temples, polished smooth where a lifetime of hats and doorframes have rubbed them. Their tail curls around a brass whistle when they need both hands free. They move in brisk, economical steps, then stop so completely that passengers sometimes mistake them for a posted sign. The unexpected detail: every few weeks they quietly mend and repaint the train's little collection of chipped toy animals, which they keep in a locked desk drawer.

Jessa is exacting about safety and unexpectedly tender toward people who feel stranded. They enjoy a clever argument when the stakes are low, but become procedural and immovable when lives are at risk. With their crew they are brisk, teasing, and protective; with officials they are formally courteous until a rule threatens a passenger, then they stop pretending the rule is reasonable. They crave companionship yet keep their grief and guilt locked away as if both were dangerous components.

Jessa learned the railway by crawling under it. Their mother, a tiefling brake mechanic, brought them up in the cramped service compartments of the long-distance locomotive called the Rookery, where Jessa learned to identify faults by smell and vibration before they could read a timetable. At nineteen, a sabotaged coupling failed during a night crossing. Jessa had seconds to choose between stopping the train in a ravine or diverting it through an abandoned mining spur. They chose the spur, saving the passengers but wrecking the engine and leaving the settlement at its end without its only winter supply shipment. The blame became a scar on their conscience, not their face. Years later they rebuilt the Rookery with an experimental arcane drive and became its conductor, insisting that nobody aboard would ever again be treated as expendable cargo. Their former mentor, Sesa, now runs a repair shed at the far end of the route and believes Jessa's strict rules have become another kind of cage. Jessa's younger sibling, Tzel, works as a courier and keeps asking for passage to places the railway authorities have forbidden. Now the drive has begun responding to a signal from the abandoned spur, though no telegraph line reaches it.