Yiso is a member of the majo zi species with a crest “made of fine white flukes” and pale silver eyes (27). They play an instrumental role in the rebellion against Jole and eventually become Kyr’s love interest. Their emotions are conveyed through a “code of crest and ears” (207). They are “curious about everything” (117). Yiso is 12 in their species’ years, which is between 15 and 20 in human years. They are very innocent and scared in the first universe.

After being abused by Avi and other humans, as well as switching to another universe, Yiso “los[es] the twitching energy” and becomes calmer and more self-possessed (272). They are “used to violence now, and it d[oes] not frighten them” (307). Yiso always retains memories from other universes; they were created by and for the Wisdom technology. They were “born to manipulate shadowspace. It’s in [them]” (366). When the Wisdom is severely damaged in the second universe, using its power inflicts physical harm on Yiso.

They don’t struggle with their mind splintering until the Wisdom destroys most of itself in the third universe. Yiso says, “You try having a god machine commit suicide in your head” (353). This causes them to be confused, rather than scared, when they return to Gaea. At the end of the novel, Kyr goes back to save Yiso, demonstrating how much she cares for them. Yiso creates a pocket universe for them until the tiny amount of the Wisdom that remains saves them.

“Mags,” or Magnus, is Kyr’s “massive, blond, square-shouldered” twin (12): They are both 17 at the time of the rebellion and are made from the same genetic material. Mags is gay, which is not allowed on Gaea, and becomes infatuated with Avi because he is the only visible gay person on the station. Mags doesn’t like fighting or killing; he asks Avi to make him a simulation of a garden without enemies. Mags also turns down the assignments that Gaea offers him: a position on any combat wing and with the secret Strike force. Instead, Mags flees to Chrysothemis and lives with his sister Ursa. He is happy in school there. However, Mags’s depression returns when he sees Avi destroy most of the majo worlds; Mags dies by suicide in the first universe. At this point, Kyr “c[an] see the shape of Mags’s unhappiness now cloaked in everything he’d said to her for years” (237).

In the second universe, Mags is named Maxwell and called “Max.” He leaves the Terran Expeditionary forces to become part of the Ziviri Jo freedom fighters. There, Mags works with Yiso, who doesn’t give Mags his memories of the first universe. However, Mags believes Kyr and Yiso when they tell him about the multiple universes. Mags helps them try to stop Jole from using the Wisdom in a similar way as Avi did in the first universe.

In the third universe, back on Gaea, Mags is still depressed, but Kyr keeps a closer eye on him. He, again, believes her about the previous universes and helps with the uprising against Jole. During the evacuation, Kyr notices that Mags is good with children and thinks that he should have been assigned to Nursery; he consistently looks out for underdogs and weaker individuals. Mags is attracted to Avi and comes out as gay in all universes. Helping with the rebellion seems to alleviate Mags’s depression in the final universe.

“Avi,” or Avicenna, is short with “red hair, a squint. Not a warbreed” (14). Avi is garrulous and brilliant: He works in Systems Wing and is adept at manipulating technology. On Chrysothemis, he gains a degree of confidence that he never found in the martial environment t of Gaea: “[D]own here in the dark of the Wisdom installation he looked confident. Like he belonged” (175). His overconfidence, and being brainwashed by Gaea, causes him to take revenge for the destruction of Earth by using the Wisdom to destroy most of the majo worlds. As with Kyr, fascist indoctrination causes him to struggle with empathy; he is an antagonist.

In the second universe, he won’t reveal his full name, so he is called “Not-Avi” (308). He gets glasses, is more physically fit, is more skilled at fighting, and is “nastier, even, because of how self-confident he [i]s” (308). He works for Jole’s Providence forces in the Terran Expeditionary and “desperately wants Jole’s approval” (311). Not-Avi repairs the Wisdom and calls himself a “master of mad alien technology” (304). His repairs enable Jole to carry out the same genocide as he did in the first universe.

In the third universe, Yiso gives Avi back his memories from the previous universes. This causes the greatest change in Avi. Kyr is able to recruit him to her group of conspirators and convince him to save as many Gaeans as possible. Avi accepts that he is part of a found family and hates Gaea. His emotional intelligence isn’t as high as Kyr’s in the final universe, but Avi makes significant positive changes.

The main antagonist in all universes is Jole, who is called “AJ” by some adults on Gaea. He has fair hair, gray eyes, an “old war injury” in his leg, and “warbreed genetics” (7). He led an uprising against the Accords that were accepted by both humans and majo after Earth was destroyed. After murdering his wife, Elora, and stealing four dreadnought spaceships, Jole co-founded Gaea, where he is the top fascist leader and a master “manipulator” (382). He kept Ursa with him and raped her; their son is named “Ally,” short for Alexander. He planned to sleep with Kyr and assigned her to Nursery Wing.

In the second universe, Jole runs Providence, which is part of the Terran Expeditionary forces. His “power and influence were built on his heroic status” as the savior of Earth (275). However, Kyr is the one who saved Earth; Jole merely took credit. He is “fatter than his Gaean self” (310). Providence secretly controls the broken Wisdom and directs its damage toward majo worlds. After Avi fixes it, Jole uses the Wisdom to destroy the same worlds as Avi destroyed in the first universe. They mirror one another in this vengeful act.

Kyr, through Val’s eyes, is able to perceive Jole clearly in the third universe. He has always been a “vindictive shit” and “a creep who gets off on power” (341, 387). Jole is not concerned with protecting humans; he “wants to rule humans” (334). In the third universe, after the Wisdom destroys most of itself and loses a cruiser to Gaea, Jole assigns Kyr to the Command Wing. He trains her, and “Kyr hate[s] that he [is] impressive” (378). In the end, he fights against the rebels and loses. He “die[s] smeared across fifteen dimensions” in the shadow engines of the dreadnoughts fighting Kyr for control of Yiso (428).

In the first universe, “Cleo,” or Cleopatra, is Kyr’s nemesis in Sparrow. She is the only person in Sparrow with “dark brown skin and tightly curling black hair” (9). The rest of the mess is white. She is a warbreed, but her genetic alterations focus on eye-hand coordination instead of size. Cleo has a “fierce spirit and perfect aim” (346). Their rivalry makes Kyr feel possessive of Cleo: “Cleo was hers” (103). After injuring Kyr in combat, Cleo allows her to escape to Chrysothemis.

In the second universe, Cleo’s full name and title are Lieutenant Cleo Alvares. She is still Kyr’s “nemesis” in that they are on opposite political sides (258), but they are friendly roommates. Both serve in the Terran Expeditionary forces, but Kyr secretly opposes Terra’s fascist government even while serving within it. In this universe, people have more freedom to date and socialize, and Cleo enjoys an active dating life while supporting Kyr dating women. Yiso gives Cleo back her memories from the first universe, and she helps Kyr and the others try to stop Jole from using the Wisdom.

In the third universe, Cleo assists Kyr and the others with the rebellion. She is assigned to Nursery Wing and can only occasionally join the conspirators’ comm channel. However, she refuses to allow Kyr to act as a lone wolf in saving Mags when he is arrested. Cleo backs up Kyr with the other Sparrows.

In the first universe, Isabelle goes by “Lisabel.” She is 17 and “cursed […] with being the prettiest of them” (335). They all know that she is doomed to be assigned to Nursery. She is very aware of station gossip and shares information about Mags turning down his assignment with Kyr. Kyr is hard on Lisabel in training but secretly has a crush on her.

In the second universe, Lisabel is named Lisa, and she goes on a date with Val. Lisa wears her dark hair loose, works at the free clinic, and is the only woman “on Hymmer with a more prestigious academic record than [Val’s]” (261). After the date, Val learns that she is Kyr and has to try and stop Jole. However, she frequently thinks about how she should call Lisa.

In the third universe, Lisabel is still “kind and beautiful” (346). She makes major decisions in the rebellion. She won’t leave without the children, and Kyr won’t leave without her. Taking the children makes the escape plan much riskier, and though Kyr agrees that it’s the right thing to do, she doesn’t think she would have the courage to do it without Lisabel’s insistence. During the escape, Russell tries to take Lisabel hostage, mirroring how he was making advances on her in the first universe. However, Lisabel is still “one of Earth’s warrior children” and shoots Russell with his own gun (416).

In the first universe, Ursa is Kyr’s sister, who was born naturally before Elora died, and looks like Kyr with gray eyes and light hair. After Jole rapes her, Ursa runs away with their child, Ally. On Chrysothemis, they start a new life. Ally wears glasses, goes to school, and “live[s] a life that d[oesn’t] have fear in it” (152). Ursa cuts off her ponytail, which “had been longer than was standard” (130). She is a brilliant historian. One of the fictional passages that Tesh includes is from Ursula’s unpublished book.

In the second universe, Ursa is Commander Ursula Marston of the Samphire. She has a good relationship with Val, and no children.

In the third universe, Ursa lives on Chrysothemis with Ally. Jole’s plan to supposedly liberate the humans on Chrysothemis is mostly to get control of his son and take revenge on Ursa for stealing Ally.

Jeanne is a warbreed, about six feet tall, and red haired. She is described as “lean and deadly, utterly and unflappably calm” (20). In the first universe, she is assigned to Ferox and gets killed there shortly after assignment; she doesn’t appear in any scenes. In the third universe, she hasn’t been assigned yet and assists with the rebellion. Jeanne’s fate in the first universe is only briefly mentioned in the second universe.

Zen/Zenobia is known for having “sharp good sense” (346). She admits, in the first and third universes, that she doesn’t like Cleo and Kyr. Because of this, she is generally quiet and keeps to herself. However, she helps with the rebellion in the end. Like Jeanne, Zen, Vic, and Arti, Zen is only briefly mentioned in the second universe.

Vic/Victoria is known for her “cleverness” (346). She is romantically involved with Arti, which is forbidden on Gaea Station, in the first and third universes.

Arti/Artemisia is known for her “protectiveness” (346). She is romantically involved with Vic in both the first and third universes. They are more open with their affection during the rebellion.