In Fantastic America, ghosts are an aberration. They exist, but they shouldn’t. Likewise, creatures of necromancy routinely ignore covenants that should keep them from entering the world of the living entirely. That puts a strain on reality no one entirely understands.
There is a lot of poorly understood or plainly unknown activity going on in my debut novel. A portion of the plot is an attempt by all the POV characters in the book to understand what is happening and why. Its obvious monsters, magic, and miracles are popping up around the world, but why? And why now? The answers will come from diligent research, along with a hefty dose of trial and error.
Zombies are a danger that left unchecked would threaten the entire planet. Wraiths, as dangerous as they can be are a limited threat. Ghosts although definitely dead, don’t follow the pattern of the others. In fact, they were here throughout the bleak times of no magic. What sense does any of that make?
The greatest threat from the characters limited understanding, would be someone who could control the dead. Someone who could direct zombies, control wraiths, and expand the list of monsters already dead but still extremely active. That’s the very definition of necromancy.