The Lunae Libri is the Caster library in Gatlin.
The Keeper of the Lunae Libri is Marian Ashcroft, originally run by Ethan's late mother Lila Evers, and the Keeper in training was Liv. It is shown to be underground full of enchanted books and has catacombs and tunnels so long and winding that even Marian, Keeper of it for years, hasn't seen them all.
It contains numerous books through the years about the Caster world such as cast books (including books from Babylonian times and from Assyria), Dark and Light talismans, caster scrolls, and etc. The cast books and caster scrolls can't be touched by mortals or it will burn their hands. Olivia Durand, was originally being trained to be the next fellow Keeper of the Caster library (as Marian was the current one being in charge of it) until she was expelled from her soon-to-have-been position for participating in a Cast with Ethan, since Keepers are not to become involved in such a thing, only learn about it. There are only a few known cast books and scrolls such as Casting, A Brief Historie; Castying to Creyate & Confounde, Casting the Confederacy, The Complete Guide to Poisonous Herbiage and Verbiage, Toes: To Caste Hair on Your Maiden's. Tongues for Binding and Casting, Toffee: Casts Hidden Inside, and Destruction of Mortal Life, Total.