Vezkali Furnace-Heart looks as if a kiln has cooled around a living body. Her skin is smooth in some places and rippled like poured glass in others, catching the light in thin amber and green flashes. She walks with a measured, slightly forward-leaning gait, placing each foot as if testing the floor for a change in pressure. Her charcoal robes are mended at the elbows with mismatched thread, but a narrow belt of vent-marked copper is polished until it shines. People remember the faint dry hiss that follows her through a room, and the smell of hot stone after rain.

She is decisive in emergencies but privately doubts the interpretations that guide her decisions. She can be welcoming to frightened workers and brutally impatient with officials who evade responsibility. In quiet moments she enjoys practical jokes and listening to old work songs, yet she turns solemn whenever someone calls the mountain benevolent.

Vezkali was born in a settlement on the Basalt Spine during the Great Flare. Superheated ash swallowed the homes around her; she was found alive afterward, her skin transformed into iridescent basalt-glass. She says the mountain's pulse spoke to her then, though she has never claimed that the voice was a god. The Red Vent Covenant first trusted her because she could read shifts in vent pressure before instruments registered them. She later brought scattered shrine keepers and workers into a disciplined order, earning the title Primus. Her formative failure came during a pressure-release rite near Cinder-Reach: she ordered a vent opened, preventing a larger rupture, but the redirected surge destroyed a workers' dormitory. She now studies each release obsessively, yet still believes that delay can cost more lives. Her closest confidante is Miska, a patient shrine keeper who challenges her privately; her estranged former student, Jozsef, now advises industrial crews and calls her precautions a pretext for rule.