During the time spent in MLP fandom I met the idea of “Elements of Disharmony” for several times. And always they were too similar to their opposites. I mean, why the powers that want to destroy a society and represent various vices will cooperate with each other? Why they, being totally chaotic and destructive, will have any constant avatar, especialy a simple mortal creature? Seriously, I’ve seen Trixie as one of them in some theory.
 
Now let’s delve into the grim darkness of the lands beyond Equestria, where you can find at least pirates, conquerors and slave trade. And soooo, I think you will guess the origin of this concept. The place where these… powers dwell we know as realm of dreams, which seems to be actually a realm, from where Luna’s inner demon tried to escape into reality and where, I suppose, Twilight was alicornized. The second thing is that they more ideas than true gods with names, biographies and other stuff. And this is where they are similar to what we know: things like Tree of Harmony and Crystal Heart took their form just because of their nature, while our evil - as I said - can’t.
 

 
Fear is the oldest of them, for it is understandable even to foolish animals. This member of the Pantheon calls at the same time to such simple things as death and physical suffering, and at the same time of frightening uncertainty and aberration. He bestows his favor tyrants, who hold their own people in constant fear (one such already appeared, guess who), and also terrorists and assassins, and than more meaningless their ruthless actions are, the better.
 
Here you can see one of the biggest cults of Fear, located in the mountains among the jungles to the South of the Equestria. Under his authority, he brought together representatives of many species, some of which were here in a completely incomprehensible way, in an incredible distance from their homeland. While the lower ranks are in Holy terror before the ever-threatening divine punishment, the high revel in their power like their master, proclaiming Holy wars for the sake of Holy wars and making bloody sacrifices for the sake of bloody sacrifices. But among those few outside the dark forces who have the right to delve into their sinister secrets, this cult is much more known for its “running priests”, preachers and hunters. They are prepared here in the most severe way to go to other lands with the purpose of sometimes very, very specific.