

Harrow initially treats Gideon as a liability and disappears for long periods of time to work on her own, leaving Gideon to wander Canaan House and interact with the other Houses. The group is tasked with exploring the mansion to discover the secrets of Lyctorhood. Harrow and Gideon travel to Canaan House, a decaying mansion on the planet of the First House, where they meet the heirs and cavaliers of the other Houses. Harrow offers Gideon a commission into the Cohort if she serves as cavalier during the Emperor's trials. Her plans of fleeing to join the Emperor's armies (called the Cohort) are quickly foiled by her lifelong antagonist and heiress of the Ninth House, Harrowhark "Harrow" Nonagesimus.ĭespite their clashing personalities and mutual hatred of each other, Gideon is Harrow's only real choice of cavalier, primarily due to an atmospheric contamination incident around the time of their births that killed the rest of the Ninth House's children. The narrative begins with eighteen year-old Gideon Nav's 86th attempt to escape the Ninth House, a death cult tasked with guarding a Locked Tomb said to contain the Emperor's greatest foe, and by whom Gideon was raised in indentured servitude. Lyctors are immortal necromancers, revered as saints, who serve as the Emperor's right-hand necromancers in wars against his enemies. At the start of Gideon the Ninth, the Emperor invites the heirs of the Nine Houses and their sword-wielding bodyguards (called cavaliers ) to undergo a series of trials to become Lyctors. The Houses in turn are ruled by the Emperor, an impossibly powerful, immortal necromancer whom they have worshipped as a god for the past ten thousand years.

In the star system Dominicus, there are nine planets, each home to a great House which practices its own school of necromancy. It is Muir's debut novel and the first in her Locked Tomb series, followed by Harrow the Ninth (2020), Nona the Ninth (2022), and Alecto the Ninth (2023). Gideon the Ninth is a 2019 science fantasy novel by the New Zealand writer Tamsyn Muir.
