A colossal figure of semi-viscous magma beneath plates of black basalt, Ignis moves with a slow, deliberate shift of weight, as if each step must be approved by the seabed. Molten seams pulse at his joints and throat, brightening when he listens to the earth. White steam and small, persistent embers rise from his scalp in place of hair. He smells strongly of hot stone, sulfur, and rain striking a forge; he knows it, and turns his head aside when the scent overwhelms a visitor. When waiting, he rests his weight on the heel of his left foot and lets the other sink slightly into the ground, testing for tremors. His unexpected habit of careful hospitality shows in the little shelves he has carved into his basalt forearm, where he keeps warm stones for cold-handed guests.

Ertug is patient enough to let a frightened stranger finish speaking, yet impatient with leaders who treat a neighboring vent as someone else's problem. He is reserved in councils and unexpectedly wry around workers, but becomes blunt and immovable when the basin's stability is at stake. He prefers repair to punishment, though he will use overwhelming force when he believes hesitation will cost lives.

Ignis was born among scattered Magma-Forged families that tended the warm seabed vents of the Sovereign Basin. In his youth, he believed each vent could be guarded alone. Then a collapse buried several passages in a single night, cutting off whole families from heat and food. Ignis led a rescue through a fissure that kept widening under his feet; he reached the trapped vent-tenders, but the delay cost his sister Oruvi her life. Afterward he helped establish the Magma-Forged compact and its rule of reciprocal warning: any member who sees a dangerous change must alert every vent that depends on it, even a rival's. He became the compact's spiritual voice by learning to read pressure through his soles and to answer tremors with ritual and practical labor alike. Now he seals fractures left by reckless extraction while trying to convince the vent-tenders that warnings must extend beyond their own compact. His closest living bond is with Amina, a young route-chorister who brings him reports from Phocan barge-cities; he trusts her observations, but resents the danger she takes to gather them. The old siphon works are changing the basin's heat, and the warnings Ignis hears beneath the Crucible are growing too frequent to dismiss.