Item from The Locked Tomb by Tamsyn Muir
The Eightfold Word — the necromantic theorem that grants immortality by consuming your cavalier's soul, because the Nine Houses have never met a problem they couldn't solve by making someone else pay for it.
The Lyctor process is the series' central horror — the revelation that immortality requires murder. Specifically, the murder of the person you are closest to, the person sworn to protect you, the person whose soul becomes your fuel. The necromancer kills their cavalier, consumes their soul, and is reborn as a Lyctor — immortal, vastly powerful, and haunted. The original Lyctors were told this was the only way. It wasn't. John achieved 'perfect Lyctorhood' with Alecto by sharing souls rather than consuming hers — but he hid this from his disciples, allowing seven cavaliers to die unnecessarily. This lie is the foundation of the entire Nine Houses system and the source of every original Lyctor's ten-thousand-year trauma. Palamedes and Camilla later proved an alternative was possible by merging into Paul — a new identity where neither soul devours the other. The Lyctor process is not the only path. It was just the one the Emperor chose to teach.
Not a physical object but a ten-part necromantic mega-theorem. The process takes place in Canaan House's sealed laboratories, where ancient research materials guide the postulants toward a discovery the Emperor already knows and isn't sharing. The physical manifestation is brutal: the cavalier dies, the necromancer transforms, and their eyes change color to reflect the consumed soul.
Also known as: Lyctorhood, The Eightfold Word, Lyctoral Ascension, The Megatheorem