Essun starts to feel at home in Castrima because she doesn’t have to hide that she is an orogene. She begins teaching the orogene children. She uses the same brutal techniques she did with Nassun and rationalizes that it is the only way to teach them a lot, quickly. Most of them hate her for it, but this doesn’t bother her if it means they survive.

Alabaster is irritated Essun is wasting her time with the children—partly because he doesn’t believe any of them have natural ability, but mostly because it is interfering with her own lessons. The Fulcrum techniques of energy redistribution that Essun is teaching the children are, by design, at odds with using magic. These techniques force the user to focus on their immediate surroundings and down into the Earth, rather than up and beyond. Alabaster argues that this is all part of the larger scheme of the Guardians. They are part of the faction in the war that wants to maintain the status quo, and orogenes who can use magic would disrupt the social order the Guardians desire. She and Alabaster theorize that what is implanted in the Guardians’ brains to give them power is part of Father Earth and that it can become contaminated, causing them to switch sides and do his bidding.

Ykka comes to get Essun because Tonkee has locked herself in Castrima’s control room. Tonkee lets them in and explains what she has discovered: a deadciv ruin with similarities to the Fulcrum’s socket and other obelisk creation ruins she’s seen before. Essun is drawn to a plinth that holds six tiny iron shards—needle thin and no bigger than a thumbnail. When Ykka bans Tonkee from coming back because she doesn’t trust her, Tonkee grabs one of the metal shards and dashes from the room. The shard digs into her skin, makes its way into her bloodstream, and begins heading toward her brain. Essun attempts to grab the shard with orogeny, but the sheer anger and hatred that emanate from it cause her to drift into a fog. As a last resort, she attempts to cut it out using magic (like the way Nassun cut the harpoon in Jija’s leg) but cuts off Tonkee’s entire arm in the process.

Hoa admits he is very old, powerful, and greatly feared—a legend among stone eaters. There have been stone eaters scavenging around Castrima, slowly devouring the place. That is where Hoa has been since he disappeared; he has been killing them one by one. Some of them flee and tell him there is another old stone eater who has plans in opposition to his. This stone eater wants to kill Essun since she plans to finish Alabaster’s plan. He cannot get to Essun while Hoa is around, but he has allied with the comm of Rennanis in hopes that they finish the job for him. Hoa hopes that Essun will forgive him one day.

Six months pass with as much comfort and stability as can be expected during a Season. Tonkee’s arm is reattached with limited loss of function, and she starts an unexpected relationship with Hjarka. Lerna forgives Essun and suggests the two of them take comfort in one another. A volunteer trading party is sent to make contact with Tettehee but does not return. Alabaster’s condition continues to worsen while Essun hurriedly tries to learn all she can from him about using magic and connecting with the obelisks.

At first, it appears the comm’s main concern is finding a long-term meat supply. Then, a hunting party is attacked, and the two survivors return with a note that reads “Welcome to Rennanis”—a clear warning from a large Equatorial city everyone assumed would have been destroyed in the Rifting. Essun uses a nearby obelisk to amplify her orogenic reach, allowing her to scout significantly further than before. She follows the node network to confirm Rennanis is still there and discovers a large camp set up in the forest basin not far from Castrima. This clarifies why Castrima wasn’t able to contact Tettehee: It was under attack.

Ykka sounds the alarm and calls a comm meeting to explain the situation to everyone. The meeting is interrupted by a stone eater claiming to represent Rennanis. He assures they will be safe if they willingly join Rennanis, barring the orogenes. The stone eater is carrying an arm that Essun recognizes as Hoa’s. She cuts off the stone eater’s hand, but he reattaches it without issue and smiles at her before leaving. Essun takes Hoa’s arm back to her apartment, where she finds the rest of his damaged body in parts. Not understanding why, beyond the fact it seems to activate all the magic within him, she feeds him the remaining stone crystals he has been carrying around. Hoa’s separated parts begin to reform, and the crystalline floor of the apartment forms up around Hoa into a geode, emanating an intense heat. In the morning, Hoa emerges from it.

Nassun accompanies Schaffa and Umber on a visit to the Antarctic Fulcrum, where they meet with three seniors. Both sides maintain a façade of manners, but Nassun can feel the fear and anger from the Antarctic trio of orogenes. She greatly dislikes the place and the people, and it makes her understand her mother better than ever before. A fight ensues, and Schaffa and Umber begin scouring the administrative buildings. Before dying, one of the Fulcrum orogenes accuses Schaffa and Umber of being “contaminated.”

Nassun realizes that Schaffa has done something that makes it impossible for her to use orogeny, and he tells her to wait for them on the terrace. On her way there, she bumps into an orogene girl about her age. The girl assumes Nassun is a new “grit” (an Imperial orogene trainee) and asks if she’s had her hand broken yet. Everything suddenly clicks: The Fulcrum is why her mother never loved her and why she taught her the way she did, why her father no longer loves her, and why her brother is dead. Nassun connects to the sapphire obelisk (which is now near Jekity) and turns the entire comm to stone.

On the way back, Nassun reflects on her situation. She senses that the silver has gone quiet in Umber but not in Schaffa and that there is tension between them. One night, while Umber is away, she asks Schaffa about the thing in his head. He says it was put there when he was a child by other Guardians, but he cannot remember who created the first ones. When Schaffa falls asleep, Nassun is visited by the stone eater who interrupted the meeting in Castrima. He expresses admiration for what Nassun did at the Antarctic Fulcrum and teaches her how to relieve Schaffa’s pain temporarily. He tells her that they fight the same enemy, and Nassun decides to call him Steel. As she falls asleep that night, she notices that one of the biggest and brightest lights in the sky is moving downward rather than west to east like the rest.

Hoa states that he wants to keep telling the story in Essun’s mind and voice. He admits it is selfish, but when he speaks for himself, he does not feel like a part of her and feels lonelier.

The Hoa who emerges from the geode is no longer a child; he is a young man and has lost his previously “fleshy” skin. He has been fighting other stone eaters, and the gray one who interrupted the meeting (the one Nassun calls Steel) proved too much for him while he was in his childlike, fleshy form. He has changed back into his adult form to better protect Essun because the other stone eaters want to kill her. Essun does not understand why Hoa has taken an interest in her, but he reveals that he was the stone eater trapped inside the damaged obelisk in Allia.

The two of them head to find Ykka. She is still at Flat Top trying to convince the comm to stick together and not accept the offer to join Rennanis, and she has not eaten or slept since the previous day. Essun forces her to eat and rest, and they discuss what is happening. Hoa reveals that Steel’s ultimate goal is to prevent anyone from using the Obelisk Gate. He is part of the faction that wants to eradicate life on Earth, leaving it for the stone eaters. His plan is to use Rennanis to destroy Castrima because it would get rid of Alabaster and Essun, the only two orogenes capable of using the obelisks. Hoa is reticent to reveal his own plans and simply states he wants to help them. Ykka is reluctant to leave Castrima and trusts the comm’s stills will stick by her. Essun is less optimistic. As Essun goes to leave, Ykka asks her to ensure the other orogenes don’t incite anything, but to also prepare for the worst.