I was under the impression that the compendiums were written for
humans. Why would there be one detailing the secrets of killing and controlling them when anyone
can do that with ease, especially the various supernaturals?
If anything, the last one is just going to be about monsters in general. They all seem to be lumped together once the angels and demons started coming to the forefront anyway. I mean, there's different kinds of angels and demons, but they're all lumped together under the same title, too.