Changelings
Changelings are the peoples Celestial genetic engineering pushed sideways rather than upward. Where the same techniques produced Uranics and the Celestials themselves, Changelings were built to fill niches — labour, transport, and worse — and they take their name from the changelings of folklore. They are the Cluster’s underclass beneath even client humans, and two of their species run through the novel: the Gath and the Moaksha.
Engineered sideways
Genetic engineering in the Cluster was not only used to advance humans. Some Celestials, particularly in the Remnant Era, used it to go sideways instead — to shape people into whatever shape a job wanted. Most Changelings are hominoid, but the design goal was the niche rather than the person, and the results range from the near-human to the frankly inhuman: one species the novel shows is a transport built out of Atlas beetle ancestry, a gloss-black carapace with too many limbs and mandibles, created for combat-zone duties.
What follows from being designed is being owned. Changelings appear throughout the book as hired hands, penned stock and industrial equipment, and the courts treat them as a capability rather than a constituency — when Wynid’s court works out who could operate an Archimedes Engine, the datamaster Lord Stethos-Thierry rules out Gath and humans alike, which is part of why the plot needs a Uranic.
The Gath
The Gath are big humanoid Changelings designed for heavy manual labour, with leathery skin and a height that dwarfs humans. They were also given a neural pathology that is gentle and meek, which offsets their size — Finn calls them a lovely people. On Gondiar they were kept on to oversee civic utility androids in Santa Rosa, were exploited badly by the companies that employed them, and have largely gone.
Where they went is the part the rest of this wiki turns on. Otylia Jalgori-Tobu found the Gath at fifteen and made them her cause for life: getting them offworld and away from the prejudice that had made Gondiar unliveable for them. The Gath crew who refit the Diligent after its colonists leave for Hafnir are that plan working — a labour arrangement on the surface, an emancipation underneath.
The Moaksha and rekaul
The Moaksha are quadrupeds rather than hominoids, and they are the source of rekaul, the neural drug that later lets Ellie recover the memories Gyvoy Enfoe took from her. A group of Moaksha ended up on Anoosha, people discovered what could be taken from them, and they have been exploited ever since.
The novel does not leave that abstract. Finn finds them penned in stalls, each one held under a skull-moulded helmet clamped on with medical braces and cabled to machinery, legs fastened with lokstrips, and there is only so much rekaul that can be drawn before a Moaksha’s brain begins to deteriorate for lack of it. He cuts them loose, puts his palm to one, and gets its pain back through the contact. It is the first thing the book shows him doing with his freedom after surviving the Camurdy Mountains, and it sets the moral terms for everything he does with the Engine later.