You might want to do a little research into Ian Fleming's adversaries for James Bond.
You could sew a lot of bad guys up into one big bag of trouble.
They could deliberately use tales of mysticism and dark horror to avoid scientific scrutiny. Of course the villagers would suspect them, but be fearful.
And then there's all that economic power.
This even has a ring of the Harry Potter nemesis.
"The Undead War: Battle Between the Immortals"
"The Order of the Steel Pomegranate", they own a catering service of all things..