User blog comment:Magma MK-II/Category Cleanup (continued)/@comment-25886777-20160428172343/@comment-2059440-20160430074635

omnicidal maniac is just really a Destroyer subcat rather than actual mental illness, you could argue it is the (il)logical conclusion of nihilistic terrorism (destroying for the sake of destroying).. also we're trying *not* to use the term maniac these days, since it is a real medical condition but also a bit of an unkind slur against mental illness in general (just like "psycho").

also Pyromania, Monomania and so on are best labelled under obsessed, since they are subcats of that specific disorder.. pyromania especially is a specific obsession and monomania as used in the wiki is basically obsession with a single idea or false belief.