Gideon is an 18-year-old orphan who serves as an indentured servant on the gloomy, crypt-like planet of the Ninth House. She wears dark sunglasses and prefers wielding a heavy two-handed sword, rejecting the traditional rapier used by House cavaliers. Brash, irreverent, and openly lesbian, she dreams of escaping her desolate home to join the Emperor's military forces, the Cohort. She masks her feelings of isolation and a deep-seated survivor's guilt with sarcastic humor and defiance.

Harrowhark is the 17-year-old Reverend Daughter and acting ruler of the Ninth House. As a bone-magic prodigy, she is the most powerful necromancer her House has produced in generations. She dresses strictly in black, wears traditional skull face paint, and maintains a rigidly perfect exterior to hide profound self-loathing. She secretly animates the preserved corpses of her parents to maintain political stability and carries an enormous burden of guilt over the mass infant deaths that preceded her birth.

Palamedes is the 20-year-old Master Warden and necromancer of the Sixth House. Dressed in plain gray clothing, he approaches necromancy as a hard science rather than a religious rite. He possesses a brilliant, analytical mind that makes him the only adept Harrowhark views as an intellectual equal. Despite his vast knowledge, he is generally relaxed and approachable.

Dulcinea is the necromancer of the Seventh House. She suffers from a fatal, hereditary blood cancer that leaves her incredibly weak and prone to fainting spells. Despite her terminal illness, she shows an intense curiosity about life and death, frequently engaging Gideon in philosophical conversations while acting as a gentle, calming presence at Canaan House.

Camilla is the cavalier of the Sixth House. Like Palamedes, she wears unassuming gray clothing. She is exceptionally quiet, rarely speaking unless necessary, and fights with a brutally effective, straightforward style that contrasts heavily with the flamboyant dueling techniques of the other cavaliers.

Ianthe is the 21-year-old Princess of the Third House and its official necromancer. Visually, she is the pale, unassuming shadow of her radiant twin sister. She tends to observe from the periphery, absorbing information while allowing her sister to command the room's attention.

Coronabeth is the Crown Princess of the Third House. She is exceedingly beautiful, charismatic, and naturally commands attention wherever she goes. She represents the wealth and glamour of the Third House, operating as the social face of their trio at Canaan House.

Naberius is the cavalier of the Third House. He is a highly trained, textbook duelist who fights strictly according to established fencing manuals. He often tries to insert himself into the squabbles between the twin princesses, though his interventions are usually unwelcome.

Protesilaus is the cavalier of the Seventh House. He is a massive, heavily armored warrior who rarely speaks, acting as a stoic and imposing guard for his dying necromancer.

Cytherea is one of the original eight Lyctors who helped the Emperor save humanity ten thousand years ago. Originating from the Seventh House, she has suffered from a debilitating illness for millennia, enduring a painful immortality in service to the God of the Nine Houses.

Isaac is the teenage necromancer of the Fourth House. Youthful and inexperienced, he relies heavily on the older members of the Fifth House for guidance as he attempts to navigate the dangerous trials of Canaan House.

Jeannemary is the teenage cavalier of the Fourth House. She is enthusiastic, easily impressed by displays of physical strength, and harbors a tragic past involving parents lost to the Emperor's wars.

Abigail is the necromancer of the Fifth House. An expert historian and skilled spirit summoner, she treats the expedition to the First House as an academic opportunity. She is maternal and protective, actively shielding the teenage representatives of the Fourth House from danger.

Magnus is the cavalier of the Fifth House and Abigail's husband. He is the oldest cavalier present at Canaan House and possesses a genuinely friendly, outgoing demeanor. He actively tries to bridge the social gaps between the isolated Houses.

Judith is the necromancer of the Second House. She approaches the trials at Canaan House with the discipline of a military commander, favoring order, protocol, and a direct chain of command back to the Cohort.

Dyas is the cavalier of the Second House. She fights with the tight, focused form of a professionally trained military duelist, relying on Cohort training rather than intuition or brute force.

Silas is the necromancer of the Eighth House. Dressed in white clothing and chainmail, he operates as a strict religious zealot. He specializes in soul siphoning, a dangerous form of magic that drains energy directly from his cavalier to power his spells.

Colum is the cavalier of the Eighth House. He endures significant physical toll to serve as a conduit for his necromancer's siphoning magic, yet he maintains his honor and keeps his given word even when it conflicts with his master's hostility.

Teacher is the head priest of the First House. He manages the skeletal servants that maintain the massive, decaying facility. He insists there are no formal rules to the Emperor's trials beyond requiring permission to open locked doors, though he clearly harbors deep fears about the facility's underground laboratories.

Crux is the marshal of the Ninth House. He despises Gideon, viewing her as an unnatural foundling and a profanity against the solemn nature of their House. He is fanatically devoted to Harrowhark and the preservation of Ninth House secrets.

Aiglamene is the Captain of the Guard for the Ninth House and Gideon's primary combat instructor. Though strict, she genuinely cares for Gideon and sees the young woman's potential, believing that becoming a cavalier is Gideon's only chance to escape a slow death on their desolate planet.

Ortus is the official cavalier of the Ninth House. Unlike the martial warriors expected of his station, he is deeply afraid of death and completely unwilling to participate in the dangerous trials at Canaan House.

Glaurica is Ortus's mother. Originally from the Eighth House, she married into the Ninth but refuses to let her son die in service to the Nonagesimus family, prompting her to steal Gideon's escape shuttle.

Priamhark is the deceased Reverend Father of the Ninth House. Driven by desperation to restore his House's political standing, he orchestrated a horrific mass casualty event to ensure his child would be a necromantic prodigy, ultimately taking his own life out of guilt.

Pelleamena is the deceased Reverend Mother of the Ninth House. She shared in the atrocious decisions that led to Harrowhark's immense power, choosing to die by suicide when her young daughter discovered the Locked Tomb.

Also known as the Necrolord Prime, the Emperor is revered as God by the Nine Houses. Ten thousand years ago, he saved humanity through a massive necromantic resurrection. He now resides on a flagship, managing a centuries-long interstellar war and seeking new immortal Lyctors to replace those he has lost.