Ok, reading rituals something occurred to me: most of them appear to have been written as if for normal, magically illiterate humans. I'm starting to think on the idea of a ritual that was written for someone or something that already knew magic, and thus contained casual references to things that seemed impossible to the reader. The fear coming from the question of who or what the thing is that could even use the ritual.
As with many of my ideas, I'm afraid that this would seem cheesy and unscary, but I thought I'd get some opinions.
One example I've considered is that the ritual requires the thumb of a dead man, and the tongue of a live man. It then specifies than when the thumb was taken the dead man must have been alive, and when the tongue was taken the live man must have been dead, as if making a living person dead, and making a dead person alive, are equally simple.