The "anti-Sanctuary" (a term coined by Skulduggery Pleasant) is an organisation without an official name, with the goal to force a war between the sorcerers and the mortals, where the sorcerers would triumph. It had been working in secret for decades and was discovered only recently by Skulduggery.
With the help of Valkyrie Cain and Omen Darkly, Skulduggery manages to find and take down many of the anti-Sanctuary's members, but not before they can resurrect Abyssinia, Skulduggery's evil ex-girlfriend.
Parthenios Lilt, a teacher at Corrival Academy, is sent to recruit new members at the school. Lilt is a history teacher and so forms a history study group called "Arcanum's Scholars“, named after an explorer called Rebus Arcanum. All members of the study group are chosen for their open dislike towards mortals; they meet in the library and hold hushed discussions. Students in this group include Jenan Ispolin, Colleen Stint and Bryon Grace.
Lethe calls the students of Arcanum's Scholars "First Wave", meaning they will form the first strike against the mortals in the upcoming war.