Essun
The orogene protagonist, who spends the book inside the geode comm of Castrima, learning from the dying Alabaster while still intent on finding her daughter. She masters the silver threads of magic, and at the climax opens the Obelisk Gate, petrifying every living person in Rennanis at the cost of her right arm turning to stone.
Nassun
Essun's roughly ten-year-old daughter, a prodigy perhaps more naturally gifted than her mother, taken south by her father in search of a supposed cure for orogeny. At Found Moon she blossoms under Schaffa's care, annihilates the Antarctic Fulcrum, turns her murderous father to stone, and ends the book drawn toward Steel's plan to crash the Moon into the world.
Alabaster
Essun's onetime mentor and lover, the most powerful orogene alive, who tore the continent open at Yumenes and is now calcifying piece by piece. He passes on the truth about magic, Father Earth, the lost Moon, and the Obelisk Gate, then dies stopping Essun's rampage on the night Castrima turns on itself.
Schaffa
The Guardian who once trained Essun, his memory mostly erased after he nearly drowned at Meov, now the founder of Found Moon at the comm of Jekity. The corestone in his skull carries Father Earth's will and keeps urging him to kill Nassun, yet his tenderness toward the girl is real and he becomes her fiercest protector.
Hoa
The stone eater who narrates Essun's story, still wearing the shape of a strange pale child when the book opens. After the gray envoy leaves him dismembered, he regrows inside a crystal cocoon and emerges as a figure of black marble, then repeatedly saves Essun during the Battle of Castrima.
Jija
Essun's husband and Nassun's father, who beat his toddler son Uche to death upon learning the boy was an orogene, then fled south with Nassun chasing a rumored cure. Never able to love the daughter he actually has, he finally attacks her with a knife, and she turns him to stone with the sapphire obelisk.
Steel
A wholly gray stone eater who delivers Rennanis's terms to Castrima while carrying Hoa's severed arm, demanding the comm's orogenes be given up to die. He later applauds Nassun's destruction of the Antarctic Fulcrum and begins steering her toward dropping the Moon onto the Earth to end all suffering.
Ykka
Castrima's leader, an orogene living openly, who ropes Essun onto the comm's ruling council. She executes Cutter with her own hands to defuse a mob, puts Rennanis's offer to a comm-wide vote, and during the battle teaches Essun the cooperative art of yoking orogenes together into one network.
Tonkee
The eccentric geomest who holes up in Castrima's ancient control room, where she grabs a rusted iron needle that burrows into her arm. Essun can only save her by using magic to amputate the limb.
Antimony
The stone eater who attends the dying Alabaster, consuming each part of him as it turns to stone. After his death she bears his body away, leaving Essun his rings and word that the onyx is the key, and she remakes him as a stone eater of pale alabaster.
Lerna
Castrima's healer, to whom Hoa carries the unconscious Essun after the battle and the opening of the Gate. Hoa quietly admits to Lerna that Essun will insist on chasing after Nassun.
Uche
Essun's toddler son, beaten to death by Jija upon the discovery that he was an orogene, the killing that set Essun walking. His death launches both threads, driving Essun's search northward while Nassun's story begins on the very day he dies.
Eitz
The oldest orogene boy at Found Moon. When he tries to wake Nassun from a nightmare while she is connected to an obelisk, she lashes out reflexively and turns him to stone, deepening the rift between her and Jija.