But the sacramentals used against him are Catholic (and in Romania Orthodox).
I didn't read all of it, but the first two pages of [1] demonstrate how the book is "Catholic" as opposed to Anglican, with the protagonist feeling awkward, as an Anglican, at the icons and crucifixes used as (in the book effective) protection.
Keep in mind, for the purposes of the book Catholicism and Orthodoxy can be considered the same as we both believe in icons, consecrated sacraments, apostolic succession, transubstination, etc