Ykka now leads Essun and the others into the house where the three women first emerged from. Inside is a stairway leading down into the earth, apparently shaped by an orogene out of solid granite. Ykka says that this and other entrances have been there for centuries, built by other people who were seemingly smarter about using orogenes than Sanze is. Essun disagrees, and Ykka asks if she was trained at the Fulcrum, since all Fulcrum orogenes seem to talk like this. Essun admits that she was. As they go down the steps, they encounter three people guarding what seems to be a drafty cellar, and Essun realizes that these are the comm’s gate guards: the abandoned town on the surface is just camouflage, and the actual comm is below.
Even after all that she’s experienced, Essun still defaults to the traditional wisdom of stonelore and the Fulcrum, assuming that the current system is the only one that works. This seeming character incongruity might be a result of the novel’s structure. The protagonist has three different identities, but because their storylines take place simultaneously, the book cannot give away too much information and spoil the novel’s mysteries. So, Essun must learn the same kinds of lessons as Damaya.
Ykka leads them on, into a tunnel that appears to be an old mine shaft. After walking for a long while, Essun asks where the red-haired stone eater is, and Ykka implies that she prefers to travel through stone, rather than walking. But then Ykka looks at Hoa, who is walking down the steps with them, and seems surprised. They then enter another tunnel, as Tonkee wonders aloud at the ancient nations that must have built these mines and passages. Tonkee then says that the big earthquake up north—which Ykka says they’ve been calling the “Yumenes Rifting”—should have destroyed this place, but Ykka responds that she didn’t let it. And in the future, she declares, there will always be other orogenes to do the same.
Castrima is clearly another comm—like Meov—that goes against the established wisdom of stonelore and Sanzed history, but that also has its own ancient and mysterious history outside of the Sanzed narrative. Just as Antimony brought Syenite and Alabaster through the earth to Meov, so the red-haired stone eater travels with greater ease through solid rock than through the air. This highlights how different Hoa is from other stone eaters, as he moves around like a normal human child.
Tonkee, who has still been asking questions and looking around in wonder, now asks Ykka how she’s been getting all the orogenes to gather here. Ykka says that it’s something she discovered that she could do years ago, and she now demonstrates it: Essun suddenly feels like she’s slipping downhill, toward Ykka herself. Ykka stops and then confirms that only roggas feel this, along with stone eaters, as she discovered later.
The Fulcrum taught orogenes like Syenite and Alabaster incredible power and control, but there are other aspects to orogeny that it seemingly ignored (whether purposefully or not), like the ability that Ykka demonstrates here. This also seems to further the idea that stone eaters are drawn to orogeny or to specific orogenes.
The group continues walking, and Essun estimates that they are now at least a mile below the earth’s surface. As they start to hear and smell people ahead, they fully appreciate what Castrima is: an entirely underground comm. Essun and Tonkee are disbelieving at first, until they finally enter and fall silent in awe. They are inside a massive geode, with crystals the size of buildings jutting out from its walls, and a city has been built among and into the crystals themselves. It’s incredibly beautiful.
It has seemed clear from the start that Castrima must be an underground comm, but for people like Essun and Tonkee who are so steeped in the reasoning of stonelore and the Stillness, this is such a radical idea that they don’t consider it until they see it for themselves. The book creates another fascinating alien world here: an enormous geode with a city built inside it.
Ykka admits that they have only built the latest additions, and they still don’t know how past people hollowed the crystals into buildings without breaking them. There are all kinds of systems in place that they don’t understand, she says: pumping out bad air, diverting an underground spring in for water, and creating electric power with a turbine. Most of it was built before the Sanzed Empire began. Tonkee notices that the crystals themselves are glowing, and Ykka says that this is another thing they have no explanation for.
The novel’s world continues to expand, both in terms of fantastical settings and the acknowledged history of the society that the characters inhabit. Castrima becomes another place that seems to exist entirely outside of stonelore and Sanze. Both the societal structure of this comm and the physical structure of the space go against and undermine the established knowledge of Sanze society and beliefs.
When they first discovered this place, Ykka explains, it was full of ancient skeletons. Because of this, no one was willing to live there for a long time, and they only used it as a cache for supplies. During the last Season, however, the aboveground comm of Castrima was burned to the ground, and the survivors had no choice but to hide underground. This failed, as well, because none of the mechanisms worked in the geode, and generations passed until Ykka’s orogenic great-grandmother figured out why. Shocked, Essun now realizes that all the mechanisms run on orogeny. Ykka says that it seems so, but still, no one is sure why or how.
This is another example of how orogeny does not need to be treated as something monstrous and deadly, but potentially as a special skill to be valued and elevated. The current societies of the Stillness maintain the Sanzed worldview, but it becomes increasingly clear that other past civilizations treated orogenes in very different ways.
After taking all of this in, Essun finally introduces herself, giving only the name “Essun,” which itself is a lie, she thinks. Tonkee and Hoa introduce themselves as well. Ykka then welcomes them to Castrima and says that their comm is just trying to survive like everyone else, but that they’re also willing to innovate to do so. Essun immediately asks if they’ll be allowed to leave. Ykka smiles but doesn’t answer and instead directs them onward. The chapter ends with an Innovator’s quotation about sessapinae, saying that they are sensitive to seismic movements but also many other things, including other people’s emotions and celestial objects.
Here, the narrative drops a clear hint that Essun is probably the older version of Syenite and Damaya, as she thinks to herself that her current name is a false identity in some way. The passage that ends this chapter looks forward to the rest of the Broken Earth trilogy, in which the true nature of orogeny is further explored—not just as a power to affect the earth’s movements, but to sense and alter other celestial bodies and even people.