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 it the grim darkness of the lands beyond Equestria, where you can find at least pirates, conquerors and slave trade.
 
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.
 

 
Despair is often depicted as a serpent with a poisonous speech, whose whisper beckons into the dark abyss. His Kingdom is an endless, half-dead wasteland surrounded by absolute emptiness. His favorite sight - a slow and irreversible decay, unattainable goals and unrealistic desires.
 
It has no multiple cults because, being despair, it doesn’t inspire anyone to do anything in his name except the rare insane prophets who decide to rid the world of the illusion of meaning (and one of them was Stygian). Instead, it has been firmly nesting for thousands of years in shady ruins and backwoods villages, and with the advent of modern times on the outskirts of cities. Wherever the immutability of the hardships and the lack of change incline the soul to humility, the serpent finds his food.