A lieutenant commander of the Gzilt military and an accomplished musician attempting to master a piece of music written for a four-armed player. When the Gzilt Regimental High Command is destroyed on the eve of the civilisation's Subliming, Cossont is drawn into a desperate search for answers.

The avatar of the Culture ship Mistake Not..., initially appearing androgynous with bronze skin before reshaping into a handsome Gzilt male. Resourceful, witty, and capable in combat, Berdle accompanies Cossont through her mission to find QiRia's mind-state and memories. Destroyed in the final battle aboard the Equatorial 353 while protecting Cossont from Colonel Agansu's android.

A highly augmented Gzilt special forces officer under Banstegeyn's command, originally of the Home System Regiment. Carries out the destruction of General Reikl's surviving forces at Izenion, later attacks the Incast facility on Bokri where he is badly injured. His consciousness is transferred to an android body for the final assault on the Equatorial 353, where he is killed by the Mistake Not...'s nanomissiles.

A highly capable Gzilt military android assigned to protect Cossont. Frustratingly convinced that everything is a simulation due to a deeply embedded software default, he nevertheless proves useful in crisis situations, guiding their crashed shuttle to safety on Eshri. Despite repeated attempts by the Culture ship to fix his programming, he persists in treating reality as a training scenario.

Commander in Chief of the Gzilt Home System Regiment, a cool and calculating military leader who serves as Banstegeyn's chief co-conspirator. She orchestrates the attack on the Fourteenth Regiment's HQ, manages the cover-up, and positions military assets throughout the crisis. Sleeps soundly despite her role in atrocities, confessing only that she cheated her officer exam before Subliming.

A Culture ship whose full name is considerably longer than anyone cares to use. Fast, capable, and deeply invested in the unfolding crisis around the Gzilt Subliming, it serves as Cossont's primary ally and transport.

A man who has lived for nearly ten thousand years, one of the oldest humans in the galaxy. He may hold the key to a secret about the Gzilt civilisation's founding that powerful people would prefer to keep buried.

Cossont's familiar, a sentient creature in the form of a square black cape that can fly independently. Dramatic, clingy, and often annoying, Pyan provides comic relief and occasional usefulness. It enjoys playing with birds and complains frequently about danger, but shows genuine affection for Cossont after her near-death experiences.

The most powerful Gzilt politician, chair of critical transitional committees as the civilisation prepares to Sublime. Ruthless and ambitious, he orchestrates the cover-up of the Book of Truth revelation, orders the destruction of the Fourteenth Regiment's HQ, and assassinates the president to maintain control. Driven by a desire to have his name immortalised, he ultimately Sublimes with everyone else.

A short, plump Gzilt Regimental Intelligence officer who arrives to re-commission Cossont for the secret emergency. He facilitates her transport to the Fourteenth Regiment's HQ at Fzan-Juym but is pulled from the evacuation shuttle by General Reikl to make room for Cossont's escape.

General Marshal Elect of the Fourteenth Regiment, a formidable and principled officer who briefs Cossont on the Book of Truth revelation and assigns her the mission to find QiRia. She pushes Cossont to safety during the attack on Fzan-Juym and later dies defiantly aboard a solar research station, spitting at Agansu's screen before riding it into the star.

An ancient Culture citizen and former friend and lover of QiRia, woken from centuries of Storage to help locate him. Her mind-state copies are transmitted to remote bodies: one rides an aphore across a desert to consult a retired drone, and another travels to Cethyd where she is killed by hostile Oglari forces before she can extract information from QiRia.

Cossont's vain and dramatic mother, living on a superliner circling the Pinicoln Sea on Zyse. Embarrassed by her daughter's extra arms and penchant for the elevenstring, she gives oblivious media interviews and inadvertently feeds intelligence to Banstegeyn's agents. She Sublimes without Cossont, who refuses to go.

A flamboyant body artist and Master of the Revels aboard the airship Equatorial 353, host of the five-year-long Last Party circling the Girdlecity. Covered in dozens of phalluses and attended by animal-headed acolytes, he is an old acquaintance of QiRia. Unwittingly wears QiRia's removed eyes as trinkets on his charm necklace. Killed in the battle aboard the airship but later restored from a recent back-up.