Dast's gaze rarely settles on a face first. It travels around a room, measuring the gaps between chairs, the reach of a hand to a latch, and the distance from a stranger's boots to the door. Their hair is cropped close at the nape and left untidy at the crown, where chalk dust gathers in a pale, stubborn haze. A dark ink stain shadows the side of one thumb. They move with a teacher's brisk economy, stopping abruptly whenever a number or claim fails to add up. Within a minute, most people notice the dry smell of chalk and fennel tea clinging to their coat; Dast knows about the tea, but insists the chalk is someone else's.

Dast is generous with patient learners but impatient with polished arguments that leave out inconvenient facts. They are quietly warm in the classroom, brisk and incisive in a dispute, and unexpectedly playful when a student finds a clever solution. Their desire to preserve Meryet's regard pulls against their refusal to let a respected authority go unchallenged.

Dast was apprenticed to Meryet of the Deep Measure as a young adult, first carrying instruments and copying calculations, then challenging the assumptions hidden inside Meryet's elegant models. During a flood survey, Dast noticed that the measurements agreed only because the crew had excluded a low district from its map. They argued to include it; Meryet hesitated, trusting the official boundaries. The flood reached the district before the revised plan did. Dast helped evacuate families and never again mistook a clean calculation for a complete one. They left the apprenticeship without breaking with Meryet. Now Dast teaches arithmetic in a crowded room above a bakehouse and sends Meryet letters full of questions, corrections, and practical exercises. Their current trouble is that the town's toll assessor wants Dast's lesson sheets to justify a new levy, while several pupils' families need those same figures to prove they have already paid.