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.
 

 
Decadence is god, in essence, of egoism. And yet, she does not demand to worship her, and even more to the contrary - her true follower should look only at himself, and his whole life should be subordinated to his own good. What was and what will be is not important. There are no rules, no prohibitions, no higher truths. His priests are jaded, almighty aristocrats who do not want to change this way, and his preachers are just as jaded creators, who want, in search of original finds, to comprehend and express the darkest depths of their nature.
 
Surprisingly, even dragons can be inclined to such a way of life. One of their nomadic hordes once, fearing the” gift “ of gigantism, settled in the distant mountains of the East and built a culture in the image and likeness of the one whose traces were found among the high peaks. Is the excessive accumulation of treasures and demonstration of brute force, they appreciate the sophistication and mastery, while essentially remaining the equally intemperate and overbearing. And many of their works, like the hoards of wild brethren, bear the imprint of this nature and bear sinister seeds in the land where they will be if the owner suddenly wishes to part with them.