An "energumen" turns out to be a person possessed by an evil spirit, or someone who acts like they're possessed, or a fanatic.
I'm now surprised that I haven't seen this term used in fandom.
But in fact where I came across it was an L.A. Times article about Pelosi and torture, in which the article's author wrote: "I oppose the sort of witch hunt Pelosi and her energumens clearly crave."
(I ask that commenters not comment on the politics of that statement; I'm quoting it only to give an example of word use. The opinions of people quoted in this blog are not necessarily shared by the blogger.)